Fixed a wrong result from mysqld--help.test.

This bug in the code of get_column_range_cardinality() could lead to
wrong estimates of number of records in ranges for non-nullable columns.  

Sampling of selectivity of LIKE predicate.

tables retrieved by range scans.

Added comments forgotten in the previous patch. 

mysql_options() with MYSQL_OPT_USE_THREAD_SPECIFIC_MEMORY

include/mysql.h:
  Added MYSQL_OPT_USE_THREAD_SPECIFIC_MEMORY
include/mysql.h.pp:
  Updated file
sql-common/client.c:
  Marked client memory as THREAD_SPECIFIC
sql/event_db_repository.cc:
  Fixed compiler warning
sql/slave.cc:
  Marked client memory as THREAD_SPECIFIC
storage/federatedx/federatedx_io_mysql.cc:
  Marked client memory as THREAD_SPECIFIC
storage/federatedx/ha_federatedx.cc:
  Marked client memory as THREAD_SPECIFIC
storage/sphinx/ha_sphinx.cc:
  Marked client memory as THREAD_SPECIFIC

sql/keycaches.cc:
  Added free_all_rpl_filters() to be able to free all filters at cleanup
sql/keycaches.h:
  Added prototype
sql/rpl_rli.cc:
  Fixed compiler warning
sql/slave.cc:
  Free all rpl_filters at cleanup
sql/sp.cc:
  Fixed compiler warning when not all struct elements was initialized
sql/sql_acl.cc:
  Fixed compiler warning when not all struct elements was initialized
storage/perfschema/table_events_waits.cc:
  Fixed compiler warning when not all struct elements was initialized
storage/perfschema/table_events_waits_summary.cc:
  Fixed compiler warning when not all struct elements was initialized
storage/perfschema/table_ews_global_by_event_name.cc:
  Fixed compiler warning when not all struct elements was initialized
storage/perfschema/table_file_instances.cc:
  Fixed compiler warning when not all struct elements was initialized
storage/perfschema/table_file_summary.cc:
  Fixed compiler warning when not all struct elements was initialized
storage/perfschema/table_performance_timers.cc:
  Fixed compiler warning when not all struct elements was initialized
storage/perfschema/table_setup_consumers.cc:
  Fixed compiler warning when not all struct elements was initialized
storage/perfschema/table_setup_instruments.cc:
  Fixed compiler warning when not all struct elements was initialized
storage/perfschema/table_setup_timers.cc:
  Fixed compiler warning when not all struct elements was initialized
storage/perfschema/table_sync_instances.cc:
  Fixed compiler warning when not all struct elements was initialized
storage/perfschema/table_threads.cc:
  Fixed compiler warning when not all struct elements was initialized
storage/xtradb/os/os0file.c:
  Fixed compiler warning when not all struct elements was initialized

 - Fix embedded build

 - Backport disable of fallocate, it creates too short ibdata1
   when used with O_DIRECT on old kernels

 - Do not disable innodb during .deb install, we need it for
   mysql.rpl_slave_state table.

Users can set different repplication filter rules for each replication connection, in my.cnf or command line.
But the rules set online will not record in master.info, it means if users restart MySQL, these rules will lose.
So if users wantn't their replication filter rules lose, they should write the rules in my.cnf.

Users can set rules by 2 ways:
1. Online SET command, "SET connection_name.replication_filter_settings = rules;".
2. In my.cnf, "connection_name.replication_filter_settings = rules".

If no connection_name in my.cnf, this rule will apply for ALL replication connection.
If no connetion_name in SET statement, this rull will apply for default_connection_name.

The official Debian Wheezy MySQL packages have versions like 5.5.30+dfsg-xxx.
Such version is larger than 5.5.30-yyy, so apt prefers it.
So use instead 5.5.30+maria-yyy, which is larger and can be pulled in
automatically by apt.

Also included are a couple of fixes for test failures in buildbot.

Renamed the virtual method middle_point_pos for the class Field to
pos_in_interval.

Merge of 10.0-mdev26 feature tree into 10.0-base.

Global transaction ID is prepended to each event group in the binlog.

Slave connect can request to start from GTID position instead of specifying
file name/offset of master binlog. This facilitates easy switch to a new
master.

Slave GTID state is stored in a table mysql.rpl_slave_state, which can be
InnoDB to get crash-safe slave state.

GTID includes a replication domain ID, allowing to keep track of distinct
positions for each of multiple masters.

Fixed MDEV-4033 Unable to use slave's temporary directory /tmp - Can't create/write to file '/tmp/SQL_LOAD-' (Errcode: 17 "File exists")
- Cache value of check_temp_dir() to avoid race condition
- Set $rpl_server_count to avoid error in show_rpl_debug_info.inc

mysql-test/suite/multi_source/info_logs.test:
  Set $rpl_server_count
mysql-test/suite/multi_source/multisource.test:
  Set $rpl_server_count
mysql-test/suite/multi_source/relaylog_events.test:
  Set $rpl_server_count
mysql-test/suite/multi_source/reset_slave.test:
  Set $rpl_server_count
mysql-test/suite/multi_source/simple.test:
  Set $rpl_server_count
mysql-test/suite/multi_source/skip_counter.test:
  Set $rpl_server_count
mysql-test/suite/multi_source/status_vars.test:
  Set $rpl_server_count
sql/slave.cc:
  Cache value of check_temp_dir() to avoid race condition

         Syntax modified to allow statements:
               ALTER TABLE ADD/DROP COLUMN
               ALTER TABLE ADD/DROP INDEX
               ALTER TABLE ADD/DROP FOREIGN KEY
               ALTER TABLE ADD/DROP PARTITION
               ALTER TABLE CHANGE COLUMN
               ALTER TABLE MODIFY COLUMN
               DROP INDEX
         to have IF (NOT) EXISTS options.
         Appropriate implementations added to mysql_alter_table().
      
      per-file comments:
        mysql-test/r/alter_table.result
      MDEV-318 IF (NOT) EXIST clauses for ALTER TABLE (MWL #252).
              test result updated.
        mysql-test/r/fulltext.result
      MDEV-318 IF (NOT) EXIST clauses for ALTER TABLE (MWL #252).
        mysql-test/r/partition.result
              test result updated.
      MDEV-318 IF (NOT) EXIST clauses for ALTER TABLE (MWL #252).
        mysql-test/t/alter_table.test
              tests added.
      MDEV-318 IF (NOT) EXIST clauses for ALTER TABLE (MWL #252).
        mysql-test/t/fulltext.test
      MDEV-318 IF (NOT) EXIST clauses for ALTER TABLE (MWL #252).
              tests added.
        mysql-test/t/partition.test
      MDEV-318 IF (NOT) EXIST clauses for ALTER TABLE (MWL #252).
              tests added.
        sql/field.cc
      MDEV-318 IF (NOT) EXIST clauses for ALTER TABLE (MWL #252).
              create_if_not_exists field added.
        sql/field.h
      MDEV-318 IF (NOT) EXIST clauses for ALTER TABLE (MWL #252).
              create_if_not_exists field added.
        sql/partition_info.h
      MDEV-318 IF (NOT) EXIST clauses for ALTER TABLE (MWL #252).
              has_unique_name made public.
        sql/sp_head.cc
      MDEV-318 IF (NOT) EXIST clauses for ALTER TABLE (MWL #252).
        sql/sql_class.cc
      MDEV-318 IF (NOT) EXIST clauses for ALTER TABLE (MWL #252).
              create_if_not_exists inited.
        sql/sql_class.h
      MDEV-318 IF (NOT) EXIST clauses for ALTER TABLE (MWL #252).
              create_if_not_exists inited.
        sql/sql_lex.cc
      MDEV-318 IF (NOT) EXIST clauses for ALTER TABLE (MWL #252).
              check_exists inited.
        sql/sql_lex.h
      MDEV-318 IF (NOT) EXIST clauses for ALTER TABLE (MWL #252).
              check_exists inited.
        sql/sql_parse.cc
      MDEV-318 IF (NOT) EXIST clauses for ALTER TABLE (MWL #252).
        check_exists inited.
        sql/sql_table.cc
      MDEV-318 IF (NOT) EXIST clauses for ALTER TABLE (MWL #252).
              handle_if_exists_options() added.
              it's called in mysql_alter_table().
        sql/sql_trigger.cc
      MDEV-318 IF (NOT) EXIST clauses for ALTER TABLE (MWL #252).
              check_exists instead of drop_if_exists.
        sql/sql_view.cc
      MDEV-318 IF (NOT) EXIST clauses for ALTER TABLE (MWL #252).
              check_exists instead of drop_if_exists.
        sql/sql_yacc.yy
      MDEV-318 IF (NOT) EXIST clauses for ALTER TABLE (MWL #252).
              sintax modified.