MDEV-26: Global transaction ID. First alpha release.

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.

mysql-test/r/mysqld--help.result

@@ -201,6 +201,12 @@ The following options may be given as the first argument:
  --group-concat-max-len=# 
  The maximum length of the result of function 
  GROUP_CONCAT()
+ --gtid-domain-id=#  Used with global transaction ID to identify logically
+ independent replication streams. When events can
+ propagate through multiple parallel paths (for example
+ multiple masters), each independent source server must
+ use a distinct domain_id. For simple tree-shaped
+ replication topologies, it can be left at its default, 0.
  -?, --help          Display this help and exit.
  --ignore-builtin-innodb 
  Disable initialization of builtin InnoDB plugin
@@ -932,6 +938,7 @@ ft-stopword-file (No default value)
 gdb FALSE
 general-log FALSE
 group-concat-max-len 1024
+gtid-domain-id 0
 help TRUE
 ignore-builtin-innodb FALSE
 ignore-db-dirs