Make the binlog handlerton participate in START TRANSACTION WITH CONSISTENT
SNAPSHOT, recording the binlog position corresponding to the snapshot taken
in other MVCC storage engines.

Expose this consistent binlog position as the new status variables
binlog_trx_file and binlog_trx_position. This enables to get a fully
non-locking snapshot of the database (including binlog position for
slave provisioning), avoiding the need for FLUSH TABLES WITH READ LOCK.

Modify mysqldump to detect if the server supports this new feature, and
if so, avoid FLUSH TABLES WITH READ LOCK for --single-transaction
--master-data snapshot backups.

 - Test internal 2-phase commit when binlog is enabled globally, but disabled in the session
 - Test crashing at various points during commit

Remove the extra class hierarchy with classes TC_LOG_queued, TC_LOG_unordered,
and TC_LOG_group_commit, folding the code into the TC_LOG_MMAP and
TC_LOG_BINLOG classes. In particular TC_LOG_BINLOG is greatly simplified by
this, unifying the code path for transactional and non-transactional
commit.

Remove unnecessary locking of LOCK_log in MYSQL_BIN_LOG::write() (backport
of same fix from mysql-5.5).

Also fix missing zero termination in DBUG_PRINT, causing garbage output
in --debug output.

Make TC_LOG_MMAP (and TC_LOG_DUMMY) derive directly from TC_LOG, avoiding the
inheritance hierarchy TC_LOG_queued->TC_LOG_unordered.

Put the wakeup facility for commit_ordered() calls into the THD class.

Some renaming to get better names.

The main.ps_ddl test does SELECT * FROM mysql.general_log; that can be really
expensive with --valgrind if previous test cases put lots of data in the
general log since last server restart. Fix by truncating the log at test start.

Also add missing destroy of pthread_cond.

client/mysqltest.cc:
  Apply Serg's work-around for MySQL BUG#57491.
mysql-test/r/group_commit_binlog_pos.result:
  Accept different ways the server crash is detected.
mysql-test/t/group_commit_binlog_pos.test:
  Accept different ways the server crash is detected.
  Skip in row-based binlogging, as otherwise the binlog offsets will be different.

MWL#116: Efficient group commit: Fix assertion by moving init/deinit out of constructor in global static object.

BUG#26447 prefer a clustered key for an index scan, as secondary index is always slower
  ... which was fixed to cause
BUG#35850 queries take 50% longer
  ... and was reverted

and

BUG#39653 prefer a secondary index for an index scan, as clustered key is always slower
  ... which was fixed to cause
BUG#55656 mysqldump takes six days instead of half an hour
  ... and was amended with a special case workaround


sql/opt_range.cc:
  move get_index_only_read_time() into the handler class
sql/sql_select.cc:
  use cost not an index length when choosing a cheaper index

MWL#116: Efficient group commit: Fix bug that binlog pos stored by XtraDB during commit was wrong when more than one commit in group.

Now the actual binlog position for each commit is stored in THD, and XtraDB
can fetch the correct value from within commit_ordered() or commit().


mysql-test/r/group_commit_binlog_pos.result:
  Test case for XtraDB binlog position.
mysql-test/t/group_commit_binlog_pos-master.opt:
  Test case for XtraDB binlog position.
mysql-test/t/group_commit_binlog_pos.test:
  Test case for XtraDB binlog position.
sql/log.cc:
  Save binlog position corresponding to commit in THD, and make accessible to storage engine.
sql/sql_parse.cc:
  Add generic crash point for use in test cases.
storage/xtradb/handler/ha_innodb.cc:
  Update to use new method of getting current binlog position that works with group commit.
storage/xtradb/handler/ha_innodb.h:
  Update to use new method of getting current binlog position that works with group commit.

and mistakingly pulled in back for maria-5.1.50.

Fixes for bugs found by running test case for LP#608369 "Page: 1 Found wrong page type 0' on CHECK TABLE EXTENDED"
Fixed overflow when using long --debug=xxxxxx line.
Fixed that "mysqld --disable-debug --debug" works.
Ensure that MariaDB doesn't start if the Aria engine didn't start and we are using Aria for temporary tables.
More DBUG_ASSERT() and more info in debug log.


dbug/dbug.c:
  Fixed crash in mysqld caused by an overflow when using long --debug=xxxxxx line
sql/mysqld.cc:
  Fixed that "mysqld --disable-debug --debug" works.
  Documented myisam-recover=OFF option
storage/maria/ha_maria.cc:
  Ensure that MariaDB doesn't start if the Aria engine didn't start and we are using Aria for temporary tables.
storage/maria/ma_delete.c:
  Added missing write of changed key on node page.
  This could fix LP#608369 "Page: 1 Found wrong page type 0' on CHECK TABLE EXTENDED"
  Changed so that we log page numbers (not positions)
  Added KEY_OP_DEBUG_2 log entry to get more debug information into the log
storage/maria/ma_key_recover.c:
  Changed so that we log page numbers (not positions)
  In case of wrong page information after index_redo, dump pages to debug log
storage/maria/ma_loghandler.h:
  Added KEY_OP_DEBUG_2
storage/maria/ma_search.c:
  Changed so that we log page numbers (not positions)
storage/maria/ma_write.c:
  Changed so that we log page numbers (not positions)

sql/sql_parse.cc:
  Make some not commonly used functions with big local variables to separate functions to make default stack usage smaller.
  Decrease size of db_buff[] (Was bigger than needed)
  Allocate current_global_status_var with malloc().
storage/maria/ha_maria.cc:
  Don't allocate HA_CHECK on stack (it's > 100K)
storage/maria/ma_check.c:
  Removed duplicated code

- _ma_apply_redo_index: Assertion `page_offset != 0 && page_offset + length <= page_length' failed
Fixes one bug and one log assert when inserting rows:
- _ma_log_split: Assertion `org_length <= info->s->max_index_block_size' failed
- write_block_record:  Assertion '(data_length < MAX_TAIL_SIZE(block_size)' failed
Mark in recovery log where _ma_log_add() calls was done (for better debugging).

storage/maria/ma_bitmap.c:
  Don't write a head part on a tail page. (Caused an assert in write_block_record())
storage/maria/ma_delete.c:
  Mark in recovery log where _ma_log_add() calls was done
storage/maria/ma_key_recover.c:
  Mark in recovery log where _ma_log_add() calls was done
  Fixed not handled logging case for overfull index pages.
storage/maria/ma_key_recover.h:
  Mark in recovery log where _ma_log_add() calls was done
storage/maria/ma_loghandler.h:
  Mark in recovery log where _ma_log_add() calls was done
storage/maria/ma_rt_key.c:
  Mark in recovery log where _ma_log_add() calls was done
storage/maria/ma_write.c:
  Mark in recovery log where _ma_log_add() calls was done.
  Fixed wrong call to _ma_split_page() for overfull pages

The reason for this was that some bitmap test functions changed the bitmap, which caused problems when the same bitmap was used by multiple threads.


include/my_bitmap.h:
  Changed order of elements to get better alignment.
mysys/my_bitmap.c:
  Change bitmap test functions to not modify the bitmap.
  Fixed compiler errors in test_bitmap

Tweak the commit_ordered() semantics. Now it is only called for transactions
that go through 2-phase commit. This avoids forcing engines to make commits
visible before they are durable.

Also take LOCK_commit_ordered() around START TRANSACTION WITH CONSISTENT
SNAPSHOT, to get a truly consistent snapshot.

Preliminary commit for testing