All changes (except one) is of type
thd->transaction.  -> thd->transaction->

thd->transaction points by default to 'thd->default_transaction'
This allows us to 'easily' have multiple active transactions for a
THD object, like when reading data from the mysql.proc table

MDEV-22468 BACKUP STAGE BLOCK_COMMIT should block commit in the Aria engine

This is needed to ensure that mariabackup works properly with Aria tables

This code ads new calls to ha_maria::implicit_commit(). These will be
deleted by MDEV-22531 Remove maria::implicit_commit().

This patch is also pushed in 10.4. It's pushed separately in 10.5 as there
are some additional cases in 10.5 to take care of.

When merging if there is conflicts, use this code, not the 10.4 code.

- Don't use 'auto' to declare variables (lazy and makes code harder to read)
- Fixed length to use correct type

I constantly store temporary 'var' directories as var2, var3 for
comparisons and having them in citool is annyoing

This bug didn't cause any issues with current usage

The GCC __atomic_ functions were removed already in
commit 2b47f8ff,
and starting with MariaDB Server 10.4, InnoDB relies mostly
on C++11 std::atomic.

In mysql/mysql-server@17e497bdb793bc6b8360aa1c626dcd8bb5cfad1b
MySQL 5.6.3 introduced innodb_checksum_algorithm=crc32 and
implemented it for AMD64 using the SSE 4.2 instructions
(incorrectly advertised as "SSE2" in a startup message).
It was not implemented on IA-32 or on Windows.

Since MariaDB 10.2.11 commit 2401d14e
we make use of the SSE4.2 CRC-32C instructions on Windows on both IA-32
and AMD64.

Let us be consistent and implement CRC-32C for IA-32 on all
available platforms. GCC 4.8.2 and GCC 4.8.5 complain
"error: PIC register clobbered by 'ebx' in 'asm'"
so we will only enable this code for IA-32 starting with GCC 5.

Also, we will clean up the implementation further after
commit 1312b4eb.

has_sse4_2(): Replaces ut_cpuid().

ut_crc32c_8(): Replaces ut_crc32_8_hw().

ut_crc32c_64(): Replaces ut_crc32_64_low_hw(), ut_crc32_64_hw().

ut_crc32_hw(): Rewrite.

ut_crc32c_8_sw(): Replaces ut_crc32_8_sw().

ut_crc32c_64_sw(): Replaces ut_crc32_64_low_sw(), ut_crc32_64_sw().

ut_crc32_sw(): Rewrite. Avoid code bloat and do not unroll the
ut_crc32c_64_sw() loop, because no benefit has been demonstrated.

ut_crc32_init(): Only invoke ut_crc32_slice8_table_init()
if no acceleration is available.

MDEV-22451: SIGSEGV in __memmove_avx_unaligned_erms/memcpy from _my_b_write on CREATE after RESET MASTER

Merge branch '10.3' into 10.4

MDEV-22451: SIGSEGV in __memmove_avx_unaligned_erms/memcpy from _my_b_write on CREATE after RESET MASTER

Merge branch '10.2' into 10.3

MDEV-22451: SIGSEGV in __memmove_avx_unaligned_erms/memcpy from _my_b_write on CREATE after RESET MASTER

Merge branch '10.1' into 10.2

ins_node_create_entry_list(): Create dummy empty tuples for
corrupted or incomplete indexes, to avoid dereferencing a NULL
dict_field_t::col pointer in row_build_index_entry_low().

This issue was found by a crash in the test gcol.innodb_virtual_basic
when merging the fix to 10.5.

MDEV-22451: SIGSEGV in __memmove_avx_unaligned_erms/memcpy from _my_b_write on CREATE after RESET MASTER

Analysis:
========
RESET MASTER TO # command deletes all binary log files listed in the index
file, resets the binary log index file to be empty, and creates a new binary
log with number #. When the user provided binary log number is greater than
the max allowed value '2147483647' server fails to generate a new binary log.
The RESET MASTER statement marks the binlog closure status as
'LOG_CLOSE_TO_BE_OPENED' and exits. Statements which follow RESET MASTER
try to write to binary log they find the log_state != LOG_CLOSED and
proceed to write to binary log cache and it results in crash.

Fix:
===
During MYSQL_BIN_LOG open, if generation of new binary log name fails then the
"log_state" needs to be marked as "LOG_CLOSED". With this further statements
will find binary log as closed and they will skip writing to the binary log.

prepare_inplace_alter_table_dict(): In the error handling, relax
a debug assertion for the case that we did not execute
dict_stats_wait_bg_to_stop_using_table() yet.

Problem:
When handling a query like this:
  VALUES ('') UNION SELECT _utf16 0x0020 COLLATE utf16_bin;
Type_handler_string_result::Item_hybrid_func_fix_attributes()
tried to apply character set conversion Item_type_holder,
which causes a crash on DBUG_ASSERT(0) inside Item_type_holder::val_str().

Fix:
Overriding Item_type_holder's methods to avoid this, as follows:

  bool const_item() const { return false; }
  bool is_expensive() { return true; }

For no good reason, innodb_encryption_threads was limited to
4,294,967,295. Expectedly, the server would crash if such an
insane value was specified. Let us limit the maximum to 255.

The encryption threads are not doing much useful work.
They are basically only dirtying pages by performing
dummy writes via the redo log. The encryption key rotation
or the in-place addition or removal of encryption
will take place in the page cleaner.

In a quick test on a 20-core CPU (40 threads in total),
the sweet spot on an otherwise idle server seemed to be
innodb_encryption_threads=16 for the test
encryption.encrypt_and_grep. The new limit 255 should be
more than enough for even bigger servers.

fts_indexes field in fts_update_t never used. So replace fts_update_t
with doc_id_t in the code

MDEV-18838 : galera.galera_toi_truncate: Test failure: mysqltest: query 'reap' succeeded - should have failed with errno 1213

Test cleanup.

This is a new test from upstream that did not expect the correct value
of the command slot of the Dump thread when the latter gets killed.

The test is made to expect "Killed" string as the command
in show-processlist as it is supposed to when a thread gets killed.