Followup. Don't compile threadpool_unix.cc when thread pool is disabled

disable tokudb paranoid asserts

Fix the bug properly (plugin cannot be unloaded as long as it's locked).
Enable and fix the test case.
Significantly reduce number of LOCK_plugin locks for semisync
(practically all locks were removed)

~40% bugfixed(*) applied
~40$ bugfixed reverted (incorrect or we're not buggy)
~20% bugfixed applied, despite us being not buggy
(*) only changes in the server code, e.g. not cmakefiles

mysql_derived_prepare() was executed on the statement memory.
Now it is executed on the runtime memory.
All bugs induced by this were fixed.

Fix for MDEV-6493: Assertion `table->file->stats.records > 0 || error' failure, or 'Invalid write' valgrind warnings, or crash on scenario with Aria table, view, LOCK TABLES

This bug only happens in case of paritioned tables used in LOCK TABLES and implicit_commit() was called
(as part of trying to execute a CREATE TABLE withing lock tables)

The problem was that Aria could not move the tables from one transaction to the new one, as thd->open_tables contained
a partitioned tables and not an Aria table.

Fix:
- Store a list of all open tables that are part of a share in share->open_tables
- In maria::implict_commit() use transaction->used_tables & share->open_tables to find out which tables
  was part of the current transaction instead of using thd->open_tables, which may contain partitioned tables.


mysql-test/suite/maria/maria_partition.result:
  Added test case
mysql-test/suite/maria/maria_partition.test:
  Added test case
storage/maria/ha_maria.cc:
  Use trn->used tables and share->open_tables to find out which tables was part of the current transaction instead of using thd->open_tables.
storage/maria/ma_close.c:
  Remove closed table from share->open_list
storage/maria/ma_open.c:
  Add table to share->open_list
storage/maria/ma_state.c:
  Added comment
storage/maria/maria_def.h:
  Added share->open_list, a list of all tables that is using this share.

* remove incorrect assertion (it didn't take into account concurrent clients)
* fix the comment

Free the trx of the current thd (if any) in innobase_end()

MDEV-6302 Wrong result set when using GROUP BY FROM_UNIXTIME(...)+0
Fixed.

  
- adjusted a test result according to the change made for MDEV-6100;
- added explicit timezone for engines/iuds, since MTR in
  MariaDB does not set it like MySQL's, and tests with constant TIMESTAMP
  can have different outcome

MDEV-6082 Assertion `0' fails in TC_LOG_DUMMY::log_and_order on DML after installing TokuDB at runtime on server with disabled InnoDB

We don't support changing tc_log implementation at run time.
If the first XA-capable engine is loaded with INSTALL PLUGIN - disable its
XA capabilities with a warning

abort the wait loop if mysqld_safe is not running

InnoDB: Failing assertion: mutex_own(&buf_pool->LRU_list_mutex)

and

InnoDB: Assertion failure in thread 2868898624 in file buf0lru.c line 1077
InnoDB: Failing assertion: mutex_own(&buf_pool->LRU_list_mutex)

Analysis: Function buf_LRU_free_block might release LRU_list_mutex on
same cases to avoid mutex order problems, we need to take it back 
before accessing list. 

backport from 10.0 the fix for:
  MDEV-5756 CMake option to build without thread pool

issue an error for unrecognized options in the [mysqld_safe] section of my.cnf
but don't abort the script

KILL USER should ignore system threads where sctx->user=sctx->host=NULL

fix by Sriram Patil

IBUF_DUMMY table.

compression failures on insert buffer.

MySQL Bug#71095: Wrong results with PARTITION BY LIST COLUMNS()
MySQL Bug#72803: Wrong "Impossible where" with LIST partitioning
MDEV-6240: Wrong "Impossible where" with LIST partitioning
- Backprot the fix from MySQL Bug#71095.

- When traversing JOIN_TABs with first_linear_tab/next_linear_tab(), don't forget
  to enter the semi-join nest when it is the first table in the join order.
  Failure to do so could cause e.g. I_S tables not to be filled.