plugins can have unused variables too. If they use a literal "Unused"
string a compiler might or might not merge two identical strings into
one (-fmerge-constants) and depending on that the server will or will
not issue a "variable is ignored" warning.

This will allow us to in the future add better error messages why
an Aria table is crashed.

MDEV-32188 make TIMESTAMP use whole 32-bit unsigned range

- Added --update-history option to mariadb-dump to change 2038
  row_end timestamp to 2106.
- Updated ALTER TABLE ... to convert old row_end timestamps to
  2106 timestamp for tables created before MariaDB 11.4.0.
- Fixed bug in CHECK TABLE where we wrongly suggested to USE REPAIR
  TABLE when ALTER TABLE...FORCE is needed.
- mariadb-check printed table names that where used with REPAIR TABLE but
  did not print table names used with ALTER TABLE or with name repair.
  Fixed by always printing a table that is fixed if --silent is not
  used.
- Added TABLE::vers_fix_old_timestamp() that will change max-timestamp
  for versioned tables when replication from a pre-11.4.0 server.

A few test cases changed. This is caused by:
- CHECK TABLE now prints 'Please do ALTER TABLE... instead of
  'Please do REPAIR TABLE' when there is a problem with the information
  in the .frm file (for example a very old frm file).
- mariadb-check now prints repaired table names.
- mariadb-check also now prints nicer error message in case ALTER TABLE
  is needed to repair a table.

This task is to ensure we have a clear definition and rules of how to
repair or optimize a table.

The rules are:

- REPAIR should be used with tables that are crashed and are
  unreadable (hardware issues with not readable blocks, blocks with
  'unexpected data' etc)
- OPTIMIZE table should be used to optimize the storage layout for the
  table (recover space for delete rows and optimize the index
  structure.
- ALTER TABLE table_name FORCE should be used to rebuild the .frm file
  (the table definition) and the table (with the original table row
  format). If the table is from and older MariaDB/MySQL release with a
  different storage format, it will convert the data to the new
  format. ALTER TABLE ... FORCE is used as part of mariadb-upgrade

Here follows some more background:

The 3 ways to repair a table are:
1) ALTER TABLE table_name FORCE" (not other options).
   As an alias we allow: "ALTER TABLE table_name ENGINE=original_engine"
2) "REPAIR TABLE" (without FORCE)
3) "OPTIMIZE TABLE"

All of the above commands will optimize row space usage (which means that
space will be needed to hold a temporary copy of the table) and
re-generate all indexes. They will also try to replicate the original
table definition as exact as possible.

For ALTER TABLE and "REPAIR TABLE without FORCE", the following will hold:
If the table is from an older MariaDB version and data conversion is
needed (for example for old type HASH columns, MySQL JSON type or new
TIMESTAMP format) "ALTER TABLE table_name FORCE, algorithm=COPY" will be
used.

The differences between the algorithms are
1) Will use the fastest algorithm the engine supports to do a full repair
   of the table (except if data conversions are is needed).
2) Will use the storage engine internal REPAIR facility (MyISAM, Aria).
   If the engine does not support REPAIR then
   "ALTER TABLE FORCE, ALGORITHM=COPY" will be used.
   If there was data incompatibilities (which means that FORCE was used)
   then there will be a warning after REPAIR that ALTER TABLE FORCE is
   still needed.
   The reason for this is that REPAIR may be able to go around data
   errors (wrong incompatible data, crashed or unreadable sectors) that
   ALTER TABLE cannot do.
3) Will use the storage engine internal OPTIMIZE. If engine does not
   support optimize, then "ALTER TABLE FORCE" is used.

The above will ensure that ALTER TABLE FORCE is able to
correct almost any errors in the row or index data.  In case of
corrupted blocks then REPAIR possible followed by ALTER TABLE is needed.
This is important as mariadb-upgrade executes ALTER TABLE table_name
FORCE for any table that must be re-created.

Bugs fixed with InnoDB tables when using ALTER TABLE FORCE:
- No error for INNODB_DEFAULT_ROW_FORMAT=COMPACT even if row length
  would be too wide. (Independent of innodb_strict_mode).
- Tables using symlinks will be symlinked after any of the above commands
  (Independent of the setting of --symbolic-links)

If one specifies an algorithm together with ALTER TABLE FORCE, things
will work as before (except if data conversion is required as then
the COPY algorithm is enforced).

ALTER TABLE .. OPTIMIZE ALL PARTITIONS will work as before.

Other things:
- FORCE argument added to REPAIR to allow one to first run internal
  repair to fix damaged blocks and then follow it with ALTER TABLE.
- REPAIR will not update frm_version if ha_check_for_upgrade() finds
  that table is still incompatible with current version. In this case the
  REPAIR will end with an error.
- REPAIR for storage engines that does not have native repair, like InnoDB,
  is now using ALTER TABLE FORCE.
- REPAIR csv-table USE_FRM now works.
  - It did not work before as CSV tables had extension list in wrong
    order.
- Default error messages length for %M increased from 128 to 256 to not
  cut information from REPAIR.
- Documented HA_ADMIN_XX variables related to repair.
- Added HA_ADMIN_NEEDS_DATA_CONVERSION to signal that we have to
  do data conversions when converting the table (and thus ALTER TABLE
  copy algorithm is needed).
- Fixed typo in error message (caused test changes).

Remove alter_algorithm but keep the variable as no-op (with a warning).

The reasons for removing alter_algorithm are:
- alter_algorithm was introduced as a replacement for the
  old_alter_table that was used to force the usage of the original
  alter table algorithm (copy) in the cases where the new alter
  algorithm did not work. The new option was added as a way to force
  the usage of a specific algorithm when it should instead have made
  it possible to disable algorithms that would not work for some
  reason.
- alter_algorithm introduced some cases where ALTER TABLE would not
  work without specifying the ALGORITHM=XXX option together with
  ALTER TABLE.
- Having different values of alter_algorithm on master and slave could
  cause slave to stop unexpectedly.
- ALTER TABLE FORCE, as used by mariadb-upgrade, would not always work
  if alter_algorithm was set for the server.
- As part of the MDEV-33449 "improving repair of tables" it become
  clear that alter- algorithm made it harder to provide a better and
  more consistent ALTER TABLE FORCE and REPAIR TABLE and it would be
  better to remove it.

This enasures that the 'variables that only exists for compatibility'
are always kept as its default value.

Based on an idea from Sergei Golubchik

Also fixed that all unused variables are using the same variable comment.
The warning will be tested with the next commit that deprecates the
variable alter_algorithm.

MDEV-32188 make TIMESTAMP use whole 32-bit unsigned range

This was done by changing DTVAL to use longlong to internally store
the date/timestamp instead of an int.

I had to preserve the old binary representation used for dates in
TABLE_TYPE=BIN. One consequence is that TABLE_TYPE=BIN cannot support
the full date bit range.

MDEV-32188 make TIMESTAMP use whole 32-bit unsigned range

- Changed usage of timeval to my_timeval as the timeval parts on windows
  are 32-bit long, which causes some compiler issues on windows.

MDEV-32188 make TIMESTAMP use whole 32-bit unsigned range

This is done by changing my_time_t from long to unsigned long.
The effect of this is that on windows compling old clients may
get warnings of if they compare my_time_t with as signed variable.

Other things
- Removed my_time_t from include/*.pp files as it is different on windows
  and linux.
- Changed do_abi_check.cmake to first print abi_check and then the
  conflicting file (this makes it easier to find the cause of the error).

This patch extends the timestamp from
2038-01-19 03:14:07.999999 to 2106-02-07 06:28:15.999999
for 64 bit hardware and OS where 'long' is 64 bits.
This is true for 64 bit Linux but not for Windows.

This is done by treating the 32 bit stored int as unsigned instead of
signed.  This is safe as MariaDB has never accepted dates before the epoch
(1970).
The benefit of this approach that for normal timestamp the storage is
compatible with earlier version.

However for tables using system versioning we before stored a
timestamp with the year 2038 as the 'max timestamp', which is used to
detect current values.  This patch stores the new 2106 year max value
as the max timestamp. This means that old tables using system
versioning needs to be updated with mariadb-upgrade when moving them
to 11.4. That will be done in a separate commit.

- Slave_IO thread time is now reset between reading events. Before
  this commit Slave_IO always showed "Waiting for master to send
  event" and the time was from SLAVE START. Now it shows time since
  reading last event.

This is to make it easier to understand why master_pos_wait() fails in mtr.

Fixed that no tables from 'mysql' schema are included in userstat.
A beneif of this is that the server is not reading statistics tables
if mysql.proc or other tables in mysql is accessed.

Other changes:
- Do not collect index statistics for system tables like index_stats
  table_stats, performance_schema, information_schema etc as the user
  has no control of these and the generate noise in the statistics.

what is done in the plugin - stays in the plugin

and adjust the copyright year

This is to update the plugin to be compatible with Percona's
query_response_time plugin, with some additions.
Some of the tests are taken from Percona server.

- Added plugins QUERY_RESPONSE_TIME_READ, QUERY_RESPONSE_TIME_WRITE and
  QUERY_RESPONSE_TIME_READ_WRITE.
- Added option query_response_time_session_stats, with possible values
  GLOBAL, ON or OFF, to the query_response_time plugin.

Notes:
- All modules are dependent on QUERY_RESPONSE_READ_TIME. This must always
  be enabled if any of the other modules are used.
  This will be auto-enabled in the near future.
- Accounting are done per statement. Stored functions are regarded
  as part of the original statement.
- For stored procedures the accounting are done per statement executed
  in the stored procedure. CALL will not be accounted because of this.
- FLUSH commands will not be accounted for. This is to ensure that
  FLUSH QUERY_RESPONSE_TIME is not part of the statistics.
  (This helps when testing with mtr and otherwise).
- FLUSH QUERY_RESPONSE_TIME_READ and FLUSH QUERY_RESPONSE_TIME_READ
  only resets the corresponding status.
- FLUSH QUERY_RESPONSE_TIME and FLUSH QUERY_RESPONSE_TIME_READ_WRITE or
  changing the value of query_response_time_range_base followed by
  any FLUSH of QUERY_RESPOSNSE_TIME resets all status.

Various help message improvements:
* MySQL->MariaDB, mysqld->mariadbd, "mysqld daemon" -> "mariadbd process"
* typos
* don't specify defaults directly in the help message
* don't say that an option is deprecated, mark is as such
* missing spaces in the middle of the text
etc

it was a no-op, plugin variables don't have dashes

* use new deprecated printer for all deprecated server options
* restore alphabetic option sorting order
* move deprecated printer from mysqld.cc to my_getopt.c
* in --help print deprecation message at the end of the option help
* move 'ALL' help text where it belongs - to other SET options, and
  with a correct indentation.
* consistently end all or none command-line option help strings
  with a dot - my_print_help() needs that.
  It's about 50/50 now, so let's do none, less line wraps in --help
* remove trailing spaces from command-line option help strings

Currently there are mechanism to mark a system variable as
deprecated, but they are only used to print warning messages
when a deprecated variable is set.

Leverage the existing mechanisms in order to make the
deprecation information available at the --help output of mysqld by:

* Moving the deprecation information (i.e `deprecation_substitute`
  attribute) from the `sys_var` class into the `my_option` struct.
  As every `sys_var` contains its own `my_option` struct, the access
  to the deprecation information remains available to `sys_var`
  objects. `my_getotp` functions, which works directly with
  `my_option` structs, gain access to this information while building
  the --help output.

* For plugin variables, leverages the `PLUGIN_VAR_DEPRECATED` flag
  and set the `deprecation_substitute` attribute  accordingly when
  building the `my_option` objects.

* Change the `option_cmp` function to use the `deprecation_substitute`
  attribute instead of the name when sorting the options. This way
  deprecated options and the substitutes will be grouped together.

All new code of the whole pull request, including one or several files
that are either new files or modified ones, are contributed under the
BSD-new license. I am contributing on behalf of my employer
Amazon Web Services, Inc.

The problem seems to be fixed earlier in the MDEV-25829 stage branch.
Removing the --disable_view_protocol command.

A user variable and a literal with different collation
produce an illegal mix of collation error.
Rewriting the script to avoid such arguments.

Step#3 The main patch

Step#2 - Adding a new collation derivation level for CAST and CONVERT.

Now character string cast functions:
  - CAST(string_expr AS CHAR)
  - CONVERT(expr USING charset_name)

have a new collation derivation level between:

  - string literals
  - utf8 metadata functions, e.g. user() and database()

Before the change these cast functions had collation derivation equal
to table columns, which caused more illegal mix of collation conflicts.

Note, binary string cast functions:
  - BINARY(expr)
  - CAST(string_expr AS BINARY)
  - CONVERT(expr USING binary)
did not change their collation derivation, to preserve the behaviour of
queries like these:
SELECT database()=BINARY'test';
SELECT user()=CAST('root' AS BINARY);
SELECT current_role()=CONVERT('role' USING binary);

Derivation levels after the change look as follows:

  DERIVATION_IGNORABLE= 7, // Explicit NULL

  DERIVATION_NUMERIC= 6,   // Numbers in string context,
                           // Numeric user variables
                           // CAST(numeric_expr AS CHAR)

  DERIVATION_COERCIBLE= 5, // Literals, string user variables

  DERIVATION_CAST= 4,      // CAST(string_expr AS CHAR),
                           // CONVERT(string_expr USING cs)

  DERIVATION_SYSCONST= 3,  // utf8 metadata functions, e.g. user(), database()
  DERIVATION_IMPLICIT= 2,  // Table columns, SP variables, BINARY(expr)
  DERIVATION_NONE= 1,      // A mix (e.g. CONCAT) of two differrent collations
  DERIVATION_EXPLICIT= 0   // An explicit COLLATE clause

Step#1 - Changing collation derivation for string user variables
from IMPLICIT to COERCIBLE.

Retionale:

Without this preparatory change, switching the default collation for
Unicode character sets from xxx_general_ci to uca1400_ai_ci would cause
"Illegal mix of collations" errors in scenarios comparing a column with
a non-default collation to a string user variable

This is especially important for queries to INFORMATION_SCHEMA tables,
whose columns use utf8mb3_general_ci.

See the description of MDEV-25829 for more details and SQL script examples.