(This commit is exclusively for 10.1 branch, do not merge it to upper ones)

In case of a pattern of non-STMT_END-marked Rows-log-event (A) followed by
a STMT_END marked one (B) mysqlbinlog mixes up the base64 encoded rows events
with their pseudo sql representation produced by the verbose option:
      BINLOG '
        base64 encoded data for A
        ### verbose section for A
        base64 encoded data for B
        ### verbose section for B
      '/*!*/;
In effect the produced BINLOG '...' query is not valid and is rejected with the error.
Examples of this way malformed BINLOG could have been found in binlog_row_annotate.result
that gets corrected with the patch.

The issue is fixed with introduction an auxiliary IO_CACHE to hold on the verbose
comments until the terminal STMT_END event is found. The new cache is emptied
out after two pre-existing ones are done at that time.
The correctly produced output now for the above case is as the following:
      BINLOG '
        base64 encoded data for A
        base64 encoded data for B
      '/*!*/;
        ### verbose section for A
        ### verbose section for B

Thanks to Alexey Midenkov for the problem recognition and attempt to tackle,
Venkatesh Duggirala who produced a patch for the upstream whose
idea is exploited here, as well as to MDEV-23077 reporter LukeXwang who
also contributed a piece of a patch aiming at this issue.

Extra: mysqlbinlog_row_minimal refined to not produce mutable numeric values into the result file.

The issue here was that the query was using ORDER BY LIMIT optimzation where
the access method was changed from EQ_REF access to an index scan (index that would
resolve the ORDER BY clause).
But the parameter READ_RECORD::unlock_row was not reset to rr_unlock_row, which is
used when the access method is not EQ_REF access.

for internal temporary tables: don't use realpath(),
and let them overwrite whatever orphan temp files might've
left in the tmpdir (see main.error_simulation test).

for user created temporary tables: we have to use realpath(),
(see 3a726ab6, remember DATA/INDEX DIRECTORY). don't allow
them to overwrite existing files.

This bug was reported by RACK911 LABS

This reverts commit 57960211.

Remove __bss_start & Co, because systen call "write" check buffer address and return EFAULT if it is wrong.

Adding any unknown option to the "[mysqld_safe]" section makes
mysqld impossible to start with mysqld_multi. For example, after
adding the unknown option "numa_interleave" to the "[mysqld_safe]"
section, mysqld_multi exits with the following diagnostics:

[ERROR] /usr/local/mysql/bin/mysqld: unknown option '--numa_interleave'

To get rid of this behavior, this patch by default adds the "--loose-"
prefix to all unknown (for mysqld_safe) options. This behavior can be
enabled explicitly with the --ignore-unknown option and disabled with
the --no-ignore-unknown option.

Since MDEV-18778, timezone tables get changed to innodb
to allow them to be replicated to other galera nodes.

Even without galera, timezone tables could be declared innodb.
With the standalone innodb tables, the mysql_tzinfo_to_sql takes
approximately 27 seconds.

With the transactions enabled in this patch, 1.2 seconds is
the approximate load time.

While explicit checks for the engine of the time zone tables could be
done, or checks against !opt_skip_write_binlog, non-transactional
storage engines will just ignore the transactional state without
even a warning so its safe to enact globally.

Leap seconds are pretty much ignored as they are a single insert
statement and have gone out of favour as they have caused MariaDB
stalls in the past.

fil_page_decompress(): Remove a rather useless debug check.
We should have test coverage for reading page_compressed pages
from files, either due to buffer pool page eviction or due to
server restarts.

A similar check was removed from fil_space_encrypt() in
commit 0b36c27e (MDEV-20307).

The usage message for the innodb_compression_algorithm system variable
did not list snappy, which was added as an optional compression algorithm
in MariaDB 10.1.3 and might actually work since
commit 90c52e52 (MDEV-12615)
in MariaDB 10.1.24.

Unfortunately, we will include also unavailable compression algorithms
in the list, because ENUM parameters allow numeric values, and we do
not want innodb_compression_algorithm=3 to change meaning depending on
the way how the source code was compiled.

InnoDB only reserves 13 bits for the heap number in the record header,
limiting the heap number to be at most 8191. But, when using
innodb_page_size=64k and secondary index records of 7 bytes each,
it is possible to exceed the maximum heap number.

btr_cur_optimistic_insert(): Let the operation fail if the
maximum number of records would be exceeded.

page_mem_alloc_heap(): Move to the same compilation unit with the
only caller, and let the operation fail if the maximum heap number
has been allocated already.

The problem is caused by the fact that adding the
--defaults-group-suffix option to fix MDEV-18863 causes
mysqld to read all options from the appropriate sections
of the config file, including options specific to mysqld_multi.
Reading unknown options (which are not supported by mysqld)
causes mysqld to terminate with an error.

However, the MDEV-18863 problem has been completely fixed
by passing options on the command line, and now there is no
need to specify the --defaults-group-suffix option (we just
need to give priority to options passed through the command
line, so as not to break MDEV-18863).

Some tests relied on the fact that DATETIME->DATE conversion
always produce a truncation (with a warning). This is not the case
when the SQL statement is executed at current time '00:00:00' sharp.

Adding a new SET TIMESTAMP statements to make sure time is not '00:00:00'.

The test encryption.create_or_replace would occasionally fail,
because some fil_space_t::n_pending_ops would never be decremented.

fil_crypt_find_space_to_rotate(): If rotate_thread_t::should_shutdown()
holds due to innodb_encryption_threads having been reduced, do
release the reference.

fil_space_remove_from_keyrotation(), fil_space_next(): Declare the
functions static, simplify a little, and define in the same compilation
unit with the only caller, fil_crypt_find_space_to_rotate().

fil_crypt_key_mutex: Remove (unused).

Example of the failure:
http://buildbot.askmonty.org/buildbot/builders/bld-p9-rhel7/builds/4417/steps/mtr/logs/stdio
```
main.mysqld--help 'unix'                 w17 [ fail ]
        Test ended at 2020-06-20 18:51:45

CURRENT_TEST: main.mysqld--help
--- /opt/buildbot-slave/bld-p9-rhel7/build/mysql-test/main/mysqld--help.result	2020-06-20 16:06:49.903604179 +0300
+++ /opt/buildbot-slave/bld-p9-rhel7/build/mysql-test/main/mysqld--help.reject	2020-06-20 18:51:44.886766820 +0300
@@ -1797,10 +1797,10 @@
 sync-relay-log-info 10000
 sysdate-is-now FALSE
 system-versioning-alter-history ERROR
-table-cache 421
+table-cache 2000
 table-definition-cache 400
-table-open-cache 421
-table-open-cache-instances 1
+table-open-cache 2000
+table-open-cache-instances 8
 tc-heuristic-recover OFF
 tcp-keepalive-interval 0
 tcp-keepalive-probes 0

mysqltest: Result length mismatch
```
mtr: table_open_cache_basic autosized:

Lets assume that >400 are available and that
we can set the result back to the start value.

All of these system variables are autosized and can
generate MTR output differences.

Closes #1527

depending on build config the error might be hidded,
in particular liblz4.so and libjemalloc.so make it to disappear,
but with -DWITH_INNODB_LZ4=NO -DWITH_JEMALLOC=NO it reappears.

Removing the ORDER BY clause from the UNION when UNION is inside an IN/ALL/ANY/EXISTS subquery.
The rewrites are done for subqueries but this rewrite is not done for the fake_select of
the UNION.

Skip leading zeros when converting a string to decimal_t.

Problem:- rpl_parallel2 was failing non-deterministically
Analysis:-
When FLUSH TABLES WITH READ LOCK is executed, it will allow all worker
threads to complete their ongoing transactions and then it will pause them.
At this state FTWRL will proceed to acquire global read lock. FTWRL first
blocks threads from starting new commits, then upgrades the lock to block
commit of existing transactions.
  Step1:
    FLUSH TABLES WITH READ LOCK - Blocks new commits
  Step2:
    * STOP SLAVE command enables 'force_abort=1' which unblocks workers,
      they continue to execute events.
    * T1: Waits in 'record_gtid' call to update 'gtid_slave_pos' table with
      its current GTID, but it is blocked becuase of Step1.
    * T2: Holds COMMIT lock and waits for T1 to commit.
  Step3:
    FLUSH TABLES WITH READ LOCK - Waiting to get BLOCK_COMMIT.
This results in deadlock. When STOP SLAVE command allows paused workers to
proceed, workers should skip the execution of all further events, similar
to 'conservative' parallel mode.
Solution:-
We will assign 1 to skip_event_group when we are aborted in do_ftwrl_wait.
rpl_parallel_entry->pause_sub_id is only reset when force_abort is off in
rpl_pause_after_ftwrl.

/home/buildbot/buildbot/build/storage/xtradb/mtr/mtr0mtr.cc:97:37: error: invalid access to non-static data member ‘fil_space_t::latch’  of NULL object [-Werror=invalid-offsetof]

Make sure system tables aren't open, as the test kills the server

MDEV-22521 Server crashes in traverse_role_graph_up or Assertion `user' fails in traverse_role_graph_impl

The only change between Percona XtraDB Server 5.6.48-88.0
and 5.6.49-89.0 (apart from the version number change) was
percona/percona-server@25ec24092064c2ab95752705e592e0c038ec1111
which we had already addressed in
commit 7c03edf2 and
commit c0fca286.

Do not collect EITS statistics for this statement:

  ALTER TABLE t ANALYZE PARTITION p

EITS stats are currently global, not per-partition.
Collecting global stats when we are asked to process just one partition
causes issues for DBAs.

MDEV-23010 UPDATE privilege at Database and Table level fail to update with SELECT command denied to user

check both column- and table-level grants when looking for SELECT
privilege on UPDATE statement.

Fix prefix key comparison in partitioning. Comparions must
take into account no more than prefix_len characters.

It used to compare prefix_len*mbmaxlen bytes.

if mysql_create_view() is aborted when view is linked into lex
(when WSREP_TO_ISOLATION_BEGIN fails),
it should not be linked there again on err:.

fix uninitialized struct member

wait_while_table_is_used() should return an error if handler::extra() fails

Largely based on MySQL commit
https://github.com/mysql/mysql-server/commit/75271e51d60bce8683423b208cbb43b11ca6060e

MySQL Ref:
    BUG#24566529: BACKPORT BUG#23575445 TO 5.6

    (cut)
    Also, the PTR_SANE macro which tries to check if a pointer
    is invalid (used when printing pointer values in stack traces)
    gave false negatives on OSX/FreeBSD. On these platforms we
    now simply check if the pointer is non-null. This also removes
    a sbrk() deprecation warning when building on OS X. (It was
    before only disabled with building using XCode).

Removed execinfo path of MySQL patch that was already included.

sbrk doesn't exist on FreeBSD aarch64.

Removed HAVE_BSS_START based detection and replaced with __linux__
as it doesn't exist on OSX, Solaris or Windows.  __bss_start
exists on mutiple Linux architectures.

Tested on FreeBSD and Linux x86_64. Being in FreeBSD ports for 2
years implies a good testing there on all FreeBSD architectures there
too. MySQL-8.0.21 code is functionally identical to original commit.

There was no ability to set the mtr arguments of:
* --max-save-core; and
* --max-save-datadir

to 0. This is desireable in an automatied scenario where space
is limited hence targeting 10.1 branch.

We take away the 0 means unlimited aspect for these,
however, perl can handle some big numbers so they may as well be
close enough to unlimited for all meaningful purposes.