The bug could cause a crash when several connections needed
persistent statistics for the same table.

Also added a missing call of set_statistics_for_table() in the code
of the function mysql_update.

Made allocation of memory for statistical data in a table share to be thread safe.
This memory is now allocated in a special MEM_ROOT that is created for each
table share.  

Remove timed mutexes in XtraDB - obsolete feature that does not link on Windows, if plugin is build dynamically
It was already  removed from innobase in the past.

Reasons:
  - as of 5.5.27, YEAR(2) is deprecated, hence the new warning;
  - MDEV-553 - different error code/message on out-of-range autoincrement;
  - INSERT IGNORE now produces a warning if a duplicate was encountered

storage_engine tests and upstream engines/* suites went out of sync with current MariaDB code. Reasons:
  - as of 5.5.27, YEAR(2) is deprecated, hence the new warning;
  - MDEV-553 - different error code/message on out-of-range autoincrement;
  - INSERT IGNORE now produces a warning if a duplicate was encountered (change pushed along with MDEV-553)

that introduced engine independent persistent statistics.
In particular:
- added an enumeration type for possible values of the system
  variable use_stat_tables
- renamed KEY::real_rec_per_key to KEY::actual_rec_per_key
- optimized the collection of statistical data for any primary
  key defined only on one column.
  

If a query referenced some system statistical tables, but not all of them,
then executing an ANALYZE command simultaneously with this query could
lead to a deadlock.
The fix prohibited reading statistics from system statistical tables
for such queries.

Removed the function unlock_tables_n_open_system_tables_for_write()
as not used anymore.
Performed some minor refactoring of the code in sql_statistics.cc. 

engine-independent statistics.
If a table was created for InnoDB then the execution of the
ANALYZE command over this table blocked any INSERT/DELETE/UPDATE
of the table. 

engine-independent statistics.
When the primary key was dropped or changed statistics on secondary
indexes for the prefixes that included components of the primary 
key was not removed from the table mysql.index_stats.

Also fixed: in the some cases when a column was changed statistics
on the indexes that included this column was not removed from the
table mysql.index_stats.

Also disabled the test mdev-504 for --ps-protocol.

then for 5.5.28a it should be
5.5.28a-mariadb1~wheezy not 5.5.28-mariadb-a1~wheezy

MDEV-3902  Assertion `record_length == m_record_length' failed at Filesort_buffer::alloc_sort_buffer

This bug is a duplicate of mdev-3899 so adding a test case only.

  
The patch decreases the duration of LOCK_thread_count, so it is not hold during THD destructor and freeing memory.
This mutex  now only protects the integrity of threads list, when removing THD from it,  and thread_count variable.
  
The add_to_status() function that updates global status during client disconnect,  is now correctly protected by the LOCK_status mutex.

Benchmark : in a  "non-persistent" sysbench test (oltp_ro with reconnect after each query),  ~ 25% more connects/disconnects were measured

MDEV-3899  Valgrind warnings (blocks are definitely lost) in filesort on IN subquery with SUM and DISTINCT
  
Analysys:
In the beginning of JOIN::cleanup there is code that is supposed to
free all filesort buffers. The code assumes that the table being sorted
is the first non-constant table. To get this table it calls:
first_top_level_tab(this, WITHOUT_CONST_TABLES)
  
However, first_top_level_tab() instead returned the wrong table - the first
one in the plan, instead of the first non-constant table. There is no other
place outside filesort() where sort buffers may be freed. As a result, the
sort buffer was not freed, and there was a memory leak.
  
Solution:
Change first_top_level_tab(), to test for WITH_CONST_TABLES instead of
WITHOUT_CONST_TABLES.

client/mysqldump.c:
  Removed compiler warning
extra/yassl/taocrypt/include/pwdbased.hpp:
  Removed compiler warning (iterations is always unsigned)
support-files/compiler_warnings.supp:
  Ignore warnings from groff

Fixed the test to be lower-case because it fails on windows with mixed case.

mysql-test/r/create.result:
  Updated test results
mysql-test/t/create.test:
  Updated test
sql/sql_base.cc:
  Use push_internal_handler/pop_internal_handler to avoid errors & warnings instead of clear_error
  Give a warnings instead of an error for CREATE TABLE IF EXISTS
sql/sql_parse.cc:
  Check if we failed because of table exists (can only happen from create)
sql/sql_table.cc:
  Check if we failed because of table exists (can only happen from create)

Analysis:
The reason for the suboptimal plan when querying IS tables through a view
was that the view columns that participate in an equality are wrapped by
an Item_direct_view_ref and were not recognized as being direct column
references.

Solution:
Use the original Item_field objects via the real_item() method.

mysql-test/r/create.result:
  Added test case to show that CREATE TABLE also is not waiting if table exists.
mysql-test/t/create.test:
  Added test case to show that CREATE TABLE also is not waiting if table exists.
sql/sql_base.cc:
  Clear also warnings from acquire_locks if we retry.

- Added option to check_if_table_exists() to quickly check if table exists (either SHARE or .FRM)
- Extended lock_table_names() to not wait for meta data locks if CREATE IF NOT EXISTS is used.

mysql-test/r/create.result:
  New test case
mysql-test/t/create.test:
  New test case
sql/sql_base.cc:
  Added option to check_if_table_exists() to quickly check if table exists (either SHARE or .FRM)
  Extended lock_table_names() to not wait for meta data locks if CREATE IF NOT EXISTS is used.
sql/sql_base.h:
  Updated prototype
sql/sql_db.cc:
  Added extra argument to call to check_if_table_exists()

1. The PERSISTENT FOR clause of the ANALYZE command overrides
the setting of the system variable use_stat_tables: 
with this clause ANALYZE unconditionally collects persistent
statistics.
2. ANALYZE collects persistent statistics only for tables of
the USER category. So it never collects persistent statistics
for system tables.  

The adjustment was supposed to be done in the previous commit.

  table_stat  -> table_stats
  column_stat -> column_stats
  index_stat  -> index_stats
to be in line with the names of innodb statistical tables 
from mysql-5.6: innodb_table_stats and innodb_index_stats.

When inserting a record with update on duplicate keys the server calls
the ha_index_read_idx_map handler function to look for the record
that violates unique key constraints. The third parameter of this call
should mark only the base components of the index where the server is
searched for the record. Possible hidden components of the primary key
are to be unmarked.

Fixed typo (missing comma)

If connection kills itself (or own query), it will get an error consistently,
with both COM_PROCESSKILL and with "KILL [QUERY] id"

Assertion happened because sql_kill did not set OK status in diagnostic area
in the case of connection suicide (id to kill == thd->thread_id), issued 
via  COM_PROCESS_KILL , e.g using mysql_kill()

This patch ensures that diagnostic area is initialized in this specific case.

Fix of MDEV-3874: Server crashes in Item_field::print on a SELECT from a MERGE view with materialization+semijoin, subquery, ORDER BY.

The problem was that in debugging binaries it try to print item to assign human readable name to the item.
But subquery item was already freed (join_free/cleanup with full cleanup) so Item_field refers to temporary
table which memory had been already freed.