dict_stats_shutdown() can hang, waiting for timer callback to finish.
This happens because locks the same mutex, which can also used inside
timer callback, within dict_stats_schedule() function.

Fix is to make dict_stats_schedule() use mutex.try_lock() instead of
mutex.lock().

In the unlikely case of simultaneous dict_stats_schedule() setting
different timer delays, now the first one would win, which is fine.
Important is that shutdown won't hang.

We must relax too strict debug assertions. For latin1_swedish_ci,
mtype=DATA_CHAR or mtype=DATA_VARCHAR will be used instead of
mtype=DATA_MYSQL or mtype=DATA_VARMYSQL. Likewise, some changes of
dtype_get_charset_coll() do not affect the data type encoding,
but only any indexes that are defined on the column.

Charset::same_encoding(): Check whether two charset-collations have
the same character set encoding.

dict_col_t::same_encoding(): Check whether two character columns
have the same character set encoding.

dict_col_t::same_type(): Check whether two columns have a compatible
data type encoding.

dict_col_t::same_format(), dict_table_t::instant_column(): Do not
compare mtype or the charset-collation of prtype directly.
Rely on dict_col_t::same_type() instead.

dtype_get_charset_coll(): Narrow the return type to uint16_t.

This is a refined version of a fix that was developed by
Thirunarayanan Balathandayuthapani.

UPDATE, DELETE: replace linear search of current/historical records
with vers_setup_conds().

Additional DML cases in view.test

The original crash happened when async replication IO thread was updating mysql.gtid_slave_pos table. Operations on this table should remain node local, but it appears that protection (THD::wsrep_ignore_table flag) to prevent wsrep replication for this table mas missing for innodb write_row() and update_row().
It was somewhat difficult to reproduce the issue, because mtr seems to create the affected table mysql.gtid_log_pos as of Aria engine type, and Aria engine operations will not be replicated anyhow. It looks, though, that in release installation, mysql.gtid_slave_pos table is of InnoDB engine.
It was possible to trigger somewhat related problem by running test galera.galera_as_slave_gtid with configuration: gtid_pos_auto_engines=InnoDB. However, this test mode, causes earlier crash when replication background thread creates aditional table: mysql.gtid_slave_pos_InnoDB, and this table create triggered wsrep TOI replication, which also failed for assertion. Actually, async replication IO and background threads should not replicate anything to cluster.

This pull request contains new test galera.galera_as_slave_gtid_auto_engine, which basically just runs galera.galera_as_slave_gtid with configuration of gtid_pos_auto_engines=InnoDB.
Test galera.galera_as_slave_gtid is also modified for better code reuse.
Actual fix for MDEV-21096 is in storage/innobase/handler/ha_innodb.cc, where THD::wsrep_ignore_table flag is now honored before wsrep key population.
There is additional fix in sql/service_wsrep.cc where async replication IO and background threads are marked as non-local. This fences these threads out of wsrep replication altogether. Note that this change, actually makes the use of THD::wsrep_ignore-table redundant. We may want to refactor THD::wsrep_ignore_table out in the future, if there is no other use case for it in sight.

At each mini-transaction commit, the log sequence number of the
mini-transaction must be written to each modified page, so that
it will be available in the FIL_PAGE_LSN field when the page is
being read in crash recovery.

InnoDB was unnecessarily allocating redundant storage for the
field, in buf_page_t::newest_modification. Let us access
FIL_PAGE_LSN directly.

Furthermore, on ALTER TABLE...IMPORT TABLESPACE, let us write
0 to FIL_PAGE_LSN instead of using log_sys.lsn.

buf_flush_init_for_writing(), buf_flush_update_zip_checksum(),
fil_encrypt_buf_for_full_crc32(), fil_encrypt_buf(),
fil_space_encrypt(): Remove the parameter lsn.

buf_page_get_newest_modification(): Merge with the only caller.

buf_tmp_reserve_compression_buf(), buf_tmp_page_encrypt(),
buf_page_encrypt(): Define static in the same compilation unit
with the only caller.

PageConverter::m_current_lsn: Remove. Write 0 to FIL_PAGE_LSN
on ALTER TABLE...IMPORT TABLESPACE.

           in row_search_idx_cond_check

For a single table query with ORDER BY and several sargable range
conditions the optimizer may choose an execution plan that employs
a rowid filter. In this case it is important to build the filter before
calling the function JOIN_TAB::sort_table() that creates sort index
for the result set, because when this is index created the filter has
to be already filled. After the sort index has been created the
filter must be deactivated. If not to do this the innodb function
row_search_idx_cond_check() is getting confused when it has to read rows
from the created sort index by using ha_rnd_pos().
The order of actions mentioned above is needed also when processing a
join query if sorting is performed for the first non constant table in
the chosen execution plan.

Implement syntax like:

create table t1 (x int) with system versioning partition by system_time;

which will create 1 history partition and 1 current partition.
Also it is possible to specify the number of history partitions:

create table t1 (x int) with system versioning partition by system_time partitions 5;

which will create 4 history partitions (and 1 current partition).

Tests:
partition.test cases are duplicated where it is appropriate for default partitions.
partition_rotation.test cases are replaced by default partitions where possible.

Use my_localhost instead of NULL for share->hostname.

MDEV-18957 UPDATE with LIMIT clause is wrong for versioned partitioned tables

UPDATE, DELETE: replace linear search of current/historical records
with vers_setup_conds().

Additional DML cases in view.test

Closes #1405

Message "WSREP: Failed to apply write set" has been turned into an
error, but tests were not adjusted accordingly.

The block defining turn_parser_debug_on() now looks similar
in both sql_yacc.yy and sql_yacc_ora.yy.

row_log_table_get_pk_col(): read instant field value from instant
alter table when it's required.

In commit daabc5cc the libmariadb
component was accidentally downgraded. Restore the latest
libmariadb release, v3.1.5.

To reduce the difference between sql_yacc.yy and sql_yacc_ora.yy,
using yyerror() in both files, instead of MYSQLerror() and ORAerror().
The pre-processor replaces yyerror() to MYSQLerror() and ORAerror()
anyway.

Add support of referential constraints directly in column defininions:

create table t1 (id1 int primary key);
create table t2 (id2 int references t1(id1));

Referenced field name can be omitted if equal to foreign field name:

create table t1 (id int primary key);
create table t2 (id int references t1);

Until 10.5 this syntax was understood by the parser but was silently
ignored.

In case of generated columns this syntax is disabled at parser level
by ER_PARSE_ERROR. Note that separate FOREIGN KEY clause for generated
columns is disabled at storage engine level.

Currently InnoDB uses internal parser for adding foreign keys. Remove
internal parser and use data parsed by SQL parser (sql_yacc) for
adding foreign keys.

- create_table_info_t::create_foreign_keys() replacement for
  dict_create_foreign_constraints_low();
- Pass constraint name via Foreign_key object.

Temporary until MDEV-20865:

- Pass alter_info as part of create_info.

btr_cur_instant_init_low(): Accurately parse the metadata record
header for ROW_FORMAT=DYNAMIC and ROW_FORMAT=COMPACT. CHAR columns
used to be unnecessarily written as nonempty strings of bytes.

For ROW_FORMAT=REDUNDANT, we must reserve fixed-length dummy values
for the CHAR columns in the metadata record. This is because in
MariaDB Server 10.4, btr_cur_instant_init_low() will rely on
dict_index_t::trx_id_offset being accurate for the metadata record.

In MariaDB Server 10.4, btr_cur_instant_init_low() assumes that
all PRIMARY KEY columns that are internally variable-length will
be encoded in 0 bytes in the metadata record. Sometimes, CHAR
columns can be encoded as variable-length. We should not
unnecessarily reserve space for a dummy string value in the
metadata record.

Do not fail fi all the partitions were pruned out.

The fix consists of three commits backported from 10.3:

1) Cleanup isnan() portability checks

(cherry picked from commit 7ffd7fe9)

2) Cleanup isinf() portability checks

Original problem reported by Wlad: re-compilation of 10.3 on top of 10.2
build would cache undefined HAVE_ISINF from 10.2, whereas it is expected
to be 1 in 10.3.

std::isinf() seem to be available on all supported platforms.
(cherry picked from commit bc469a0b)

3) Use std::isfinite in C++ code

This is addition to parent revision fixing build failures.

(cherry picked from commit 54999f4e)

Memcpy is endian dependent, So instead of memcpy we will use int2store.
And m_metadata_size can be 0,1 or 2, And int2store will take care of it.

On order to unify the two *.yy files easier,
this patch collects all different rules to the end of *.yy files,
so the rule section looks like this:

%%
common rules
different rules

DropIndex, CreateIndex: Remove. The file row0trunc.cc only exists
in MariaDB Server 10.3 so that the crash recovery of TRUNCATE TABLE
operations from older 10.2 and 10.3 servers will work. This dead code
was being used for implementing the MySQL 5.7 WL#6501 TRUNCATE TABLE
that was replaced with a backup-safe implementation in MDEV-13564.

buf_read_ibuf_merge_pages(): Discard any page numbers that are
outside the current bounds of the tablespace, by invoking the
function ibuf_delete_recs() that was introduced in MDEV-20934.
This could avoid an infinite change buffer merge loop on
innodb_fast_shutdown=0, because normally the change buffer merge
would only be attempted if a page was successfully loaded into
the buffer pool.

dict_drop_index_tree(): Add the parameter trx_t*.
To prevent the DROP TABLE crash, do not invoke btr_free_if_exists()
if the entire .ibd file will be dropped. Thus, we will avoid a crash
if the BTR_SEG_LEAF or BTR_SEG_TOP of the index is corrupted,
and we will also avoid unnecessarily accessing the to-be-dropped
tablespace via the buffer pool.

In MariaDB 10.2, we disable the DROP TABLE fix if innodb_safe_truncate=0,
because the backup-unsafe MySQL 5.7 WL#6501 form of TRUNCATE TABLE
requires that the individual pages be freed inside the tablespace.

When commit 09af00cb
removed the crash-upgrade logic of old TRUNCATE TABLE
from MariaDB 10.2 and 10.3, it actually made the return
value of dict_drop_index_tree() redundant.

Adding:
- new class sp_expr_lex
- new grammar rule expr_lex, which includes both reset_lex()
  and its corresponding restore_lex()

Also:
- Moving a few methods from LEX to sp_expr_lex.
- Moving the code from *.yy to new method sp_expr_lex methods
  sp_repeat_loop_finalize() and sp_if_expr().

This change makes it easier to edit the related grammar
(and makes it easier to unify sql_yacc.yy and sql_yacc_ora.yy later).

Simplify task_group destructor.
No tasks must be running or queued into task group is being destroyed.