special builds UNIV_PAGECOMPRESS_DEBUG and UNIV_MTFLUSH_DEBUG).

Added a new status variable compress_pages_page_compression_error to count possible
compression errors.

unnecessary. There is a lot more index pages than there is normal pages.
Earlier all pages were compressed and this provided best performance and
compression ratio. Added status variable to show how many non index pages
are written.

MDEV-5789: race between rpl_parallel_change_thread_count and slave start upon server start without --skip-slave-start

Make sure to signal the condition variable for the thread pool after
the new threads have been added to the pool.

Thanks to user nanyi607rao, who reported this bug on maria-developers@.

When an rpl_group_info object was returned from the free list, the
rgi->deferred_events_collecting and rgi->deferred_events was not correctly
re-inited. Additionally, the rgi->deferred_events was incorrectly freed in
free_rgi(), which causes unnecessary malloc/free (or crash when re-init is not
done).

Thanks to user nanyi607rao, who reported this bug on maria-developers@.

This constant uses my_time.h, which inclusion is not desirable in nt_servc.cc

pages are compressed if false index pages are not compressed.

Fixed small output error when page_compression_level was incorrectly
given.

Reduced number of my_hash_sort_bin() calls from 4 to 1 per query.
Reduced number of memory accesses done by my_hash_sort_bin().

Details:
- let MDL subsystem use pre-calculated hash value for hash
  inserts and deletes
- let table cache use pre-calculated MDL hash value
- MDL namespace is excluded from hash value calculation, so that
  hash value can be used by table cache as is
- hash value for MDL is calculated as resulting hash value + MDL
  namespace
- extended hash implementation to accept user defined hash function

- MariaDB-5.5 part of the fix: since we can't easily fix query optimization for I_S tables, 
  run the affected-tablespaces query with semijoin=off. It happens to have a good query plan
  with that setting.
[This is a forward-port to MariaDB 10.0]

- Removed double call to trans_begin() for GTID BEGIN event
- Don't set OPTION_BEGIN before calling trans_begin() as this causes extra work in trans_begin()

sql/log_event.cc:
  Removed double call to trans_begin for GTID BEGIN event.
  Don't set OPTION_BEGIN before calling trans_begin() as this causes extra work in trans_begin().
  This was done by removing parsing of "BEGIN" and instead executing trans_begin() direct.
  This is much faster, but we lost the ability logging of possible slow "BEGIN" statements. As this should never happen it can be ignored.

mysql-test/suite/rpl/t/rpl_heartbeat_basic.test:
  Added sync_slave_with_master to remove timing problem

as it is not used/implemented.

that we can later use it to avoid unnecessary trim operations. 

Patch from Tomas Matejicek

Add missing error code to is_networ_error(), to allow slave to
automatically attempt reconnection also in this case.

The problem was when a GTID event was part of a group commit, and so contained
a commit id. The code that replaces GTID with a BEGIN event for old slaves did
not correctly handle this case.

Fix the code so that the GTID with commit id can also be properly replaced
with a BEGIN query event. The extra two bytes are in the BEGIN event replaced
with a dummy, empty time zone string.

- Make do_fill_table() use join_tab->cache_select->cond if it is present.  When 
  join_tab->cache_select->cond is present, join_tab->select_cond doesn't have any 
  conditions that are usable for I_S optimizations.

Older master has no GTID events, so such events are not available for
deciding on scheduling of event groups and so on.

With this patch, we run such events from old masters single-threaded, in the
sql driver thread.

This seems better than trying to make the parallel code handle the data from
older masters; while possible, this would require a lot of testing (as well as
possibly some extra overhead in the scheduling of events), which hardly seems
worthwhile.

- Fix valgrind failure: make test_if_order_by_key() account for extended keys 
  feature.

individual queue's. Tried to minimize memory allocation from heap
whenever it is unnecessary.