MDEV-5153: Server crashes in Item_ref::fix_fields on 2nd execution of PS with LEFT JOIN and MERGE view or SELECT SQ

1. Transformation of row IN subquery made the same as single value.
2. replace_where_subcondition() made working on several layers of OR/AND because it called on expression before fix_fields().

Singular Item_equal support added.

The problem was that during constant table substitution Item_equal become containing only one constant which was not supported internally.

Modified according to the review comment

The loop in the binary search in remove_status_vars() was
incorrectly implemented and could continue infinitely in some cases.
Rewrote the binary search code.

Delete any left-over deferred_event from rpl_group_info when
deleting the parent object, to protect against memory leaks.

Remove rpl_group_info from THD before freeing it,
to avoid access-after-free in THD.

Tested manually that crash in the middle of writing transaction on the master
does correctly cause a rollback on slave, so remove the corresponding ToDo.

Fix access of freed memory in debug builds. When deleting serial_rgi,
safe_mutex was trying to access current_thd, when that thd had just been
deleted (I hate all this current_thd and other magic thread local storage crap
used all over the code). Now delete the serial_rgi before the thd.

to be correct

An addition to fix for MDEV-5205, fixes server crash on shutdown.

Thread groups are destroyed asynchronously, that is kill server
thread sends shutdown request to all thread groups without waiting
for compeltion.

It means all_groups array must not be freed until all thread groups
are down. This patch suggests that all_groups is freed when last
thread group is destroyed.

Note 1: threadpool code doesn't surround atomic ops with atomic locks,
thus no locks for shutdown_group_count.
Note 2: this patch preserves old behaviour, but we may need to wait
until all thread groups are down before returning from tp_end().

MDEV-5217: Incorrect MyISAM event execution order causing incorrect parallel replication

In parallel replication, if transactions A,B group-commit together on the
master, we can execute them in parallel on a replication slave. But then, if
transaction C follows on the master, on the slave, we need to be sure that
both A and B have completed before starting on C to be sure to avoid
conflicts.

The necessary wait is implemented such that B waits for A to commit before it
commits itself (thus preserving commit order). And C waits for B to commit
before it itself can start executing. This way C does not start until both A
and B have completed.

The wait for B's commit on A happens inside the commit processing. However, in
the case of MyISAM with no binlog enabled on the slave, it appears that no
commit processing takes place (since MyISAM is non-transactional), and thus
the wait of B for A was not done. This allowed C to start before A, which can
lead to conflicts and incorrect replication.

Fixed by doing an extra wait for A at the end of B before signalling C.

MDEV-5217: Unlock of de-allocated mutex

There was a race in the code for wait_for_commit::wakeup().

Since the waiter does a dirty read of the waiting_for_commit
flag, it was possible for the waiter to complete and deallocate
the wait_for_commit object while the waitee was still running
inside wakeup(). This would cause the waitee to access invalid
memory.

Fixed by putting an extra lock/unlock in the destructor for
wait_for_commit, to ensure that waitee has finished with the
object before it is deallocated.

MDEV-5217: Incorrect event pos update leading to corruption of reading of events from relay log

The rli->event_relay_log_pos was sometimes undated incorrectly when using
parallel replication, especially around relay log rotates. This could cause
the SQL thread to seek into an invalid position in the relay log, resulting in
errors about invalid events or even random corruption in some cases.

include/CMakeLists.txt:
  Added handler_ername.h
include/handler_ername.h:
  Names of handler error messages
mysql-test/extra/binlog_tests/binlog.test:
  Test using handler error names
mysql-test/r/mysqltest.result:
  Update for new error message
mysql-test/t/auto_increment.test:
  Test using handler error names
mysql-test/t/auto_increment_ranges.inc:
  Test using handler error names
mysql-test/t/replace.test:
  Test using handler error names

storage/xtradb/handler/ha_innodb.cc:
  Fixed wrong last argument to buf_LRU_free_block(): The LRU chain is already locked by this function.

MDEV-5217: Last_sql_error lost in parallel replication.

For some reason, the query execution code in log_event.cc call
rli->clear_error for each event (part of clear_all_errors()).
This causes a problem in parallel replication, where the
execution in one worker thread could clear the error set by
another thread, causing the SQL thread to stop but leaving no
error visible in SHOW SLAVE STATUS.

There seems to be no reason to clear the global error code
in Relay_log_info for each event execution, from code review
and from running the test suite. So remove this clearing of
the error code to make things work also in the parallel case.

MDEV-5217: SQL thread hangs during stop if error occurs in the middle of an event group

Normally, when we stop the slave SQL thread in parallel replication, we want
the worker threads to continue processing events until the end of the current
event group. But if we stop due to an error that prevents further events from
being queued, such as an error reading the relay log, no more events can be
queued for the workers, so they have to abort even if they are in the middle
of an event group. There was a bug that we would deadlock, the workers
waiting for more events to be queued for the event group, the SQL thread
stopped and waiting for the workers to complete their current event group
before exiting.

Fixed by now signalling from the SQL thread to all workers when it is about
to exit, and cleaning up in all workers when so signalled.

This patch fixes one of multiple problems reported in MDEV-5217.

- thread_pool_size command line option upper limit increased to 100 000
  (same as for max_connections)
- thread_pool_size system variable upper limit is maximum of 128 or
  the value given at command line
- thread groups are now allocated dynamically

Different limit for command line option and system variable was done to
avoid additional mutex for all_groups and threadpool_max_size.

increase the initial ibdata1 size, as explained in MySQL-5.6 revid:kevin.lewis@oracle.com-20120802192452-kmikiz990xzje18b

"
  A maximum size of 10 Mb works in 5.1 because the initial
  required size of ibdata1 was less than 10M.  But in 5.5, a
  change was made to allocate all 128 rollback segments at
  bootstrap.  Since then, the initial size has been 10M + the
  default autoextend size of 8M. 

  In 5.6, worklog 6216 changes the autoextend size from 8M to
  64M.  This changes the initial size of ibdata1 from 18M in
  5.5 and earlier releases of 5.6 to 74M in the current
  mysql-5.6 and mysql-trunk.  So this change is especially
  needed in 5.6.
"

12M is enough to avoid autoextending during bootstrap

MDEV-5080 Assertion `strcmp(share->unique_file_name,filename) || share->last_version' fails at /storage/myisam/mi_open.c:67

extend table names discovery (ha_discover_table_names() and Discovered_table_list) to return
or optionally filter out temporary tables ("#sql..."). SHOW commands and I_S tables
typically want temp table filtered out, while DROP DATABASE wants to see them too.

additonally, remove the supression for the warning "Invalid (old?) table or database name"
from mtr, and add it to .test files as needed (we need to test that this warning
does *not* happen in drop.test)

(broken in the revid:sergii@pisem.net-20130615170931-bn2h8j30vu5bfp0t)

use the same inconsistent priv_user@host pair for SET ROLE privilege checks,
just as check_access() does

10.0 part of the task, fix system tables