The patch lifts the limitation of the current implementation
of ALTER TABLE that does not allow to build unique/primary
indexes by sort for MyISAM and Aria engines.

- Cleanup ha_cassandra::store_lock()
- Remove dummy ha_cassandra::delete_table()
- Add HA_TABLE_SCAN_ON_INDEX to table_flags()

- Register counters directly in the array passed to maria_declare_plugin. As 
  a consequence, FLUSH TABLES will reset the counters.
- Update test results accordingly.

- Partially address review feedback.
- Update cassandra.test result result
- make cassandra.test timezone-agnostic

Implement it in a different way that works on both release and debug
builds, and still uses --skip instead of --require.

have_openssl variable was ON even when OpenSSL was not used (but YaSSL was).
fix that, so that have_openssl really corresponds to OpenSSL

rename not_openssl.inc to not_ssl.inc and fix the test accordingly.

remove unused require files

MDEV-438 Microseconds: Precision is ignored in CURRENT_TIMESTAMP(N) when it is given as a default column value

For MySQL 5.6 compatibility, support precision specification in CURRENT_TIMESTAMP in
a default clause, when it's not less than the column's precision.

With MDEV-532, the binlog_checkpoint event is logged asynchronously
from a binlog background thread. This causes some sporadic failures
in some test cases whose output depends on order of events in
binlog.

Fix using an include file that waits until the binlog checkpoint
event has been logged before proceeding with the test case.

Make the commit checkpoint inside InnoDB be asynchroneous.
Implement a background thread in binlog to do the writing and flushing of
binlog checkpoint events to disk.

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.
  

Post-review changes according to Monty's review from 28/11/2012.

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.

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.