WORK WITH GTID

  Problem:  When mysqlbinlog processes and concatenates
  multiple binary log files into one output file, this
  output file is not in useful state. When it is later
  used for point-in-time recovery, it is producing
  ER_GTID_NEXT_TYPE_UNDEFINED_GROUP "ERROR 1837: When
  @@SESSION.GTID_NEXT is set to a GTID, you must explicitly
  set it to a different value after a COMMIT or ROLLBACK.
  Please check GTID_NEXT variable manual page for detailed
  explanation. Current @@SESSION.GTID_NEXT is 'xyz'".

  Analysis: When mysqlbinlog processes a GTID enabled
  binary log, it outputs SET GTID_NEXT statements. As
  GTID_NEXT is set to 'undefined' when a transaction
  commits (or DDL commits implicitly), this will leave
  GTID_NEXT as 'undefined' when the server has processed
  all output from mysqlbinlog. Also, there can be some
  anonymous statements/transactions at the beginning of
  binary log (i.e., without SET GTID_NEXT statements).   
  When mysqlbinlog processes and concatenates two (or more)
  binary log files into one output file, the combination
  (GTID_NEXT is undefined at the end of first binary log
  and second binary log can contain anonymous transactions)
  will not work and will result in ERROR 1837
  (ER_GTID_NEXT_TYPE_UNDEFINED_GROUP).
 
  Fix: When mysqlbinlog processes second binary log's
       start_log_event, it can output
       "SET GTID_NEXT=AUTOMATIC" if required i.e., if
       previous binary log is leaving the GTID_NEXT state
       in 'undefined' state. In the old code (before this
       patch), when mysqlbinlog processes multiple binary
       log files from multiple command line arguments, it
       used a new PRINT_EVENT_INFO object for each file,
       so the state at the end of the previous file is lost.
       To solve this problem, this patch changes the logic
       to use the same PRINT_EVENT_INFO structure for all
       command line arguments. And to keep track of
       gtid_next state, we are introducing
       is_gtid_next_valid and is_gtid_next_set variables.
       At the beginning of mysqlbinlog process
       is_gtid_next_set is set to false and
       is_gtid_next_valid is set to true.
       When mysqlbinlog encounters a
         i) GTID_LOG_EVENT: it sets is_gtid_next_set to
                            true and is_gtid_next_valid to
                            true.
        ii) XID_LOG_EVENT
             /end_group() : it sets is_gtid_next_valid to
                            false if is_gtid_next_set to
                            true.
       And when mysqlbinlog is processing start_log_event,
       if it finds gtid_next is not valid (i.e., undefined)
       then it produces "SET GTID_NEXT=AUTOMATIC" in the
       output file to avoid mentioned
       ER_GTID_NEXT_TYPE_UNDEFINED_GROUP error and it resets
       is_gtid_next_set to false and is_gtid_next_valid to
       true (the initial values). mysqlbinlog also produces
       'SET GTID_NEXT=AUTOMATIC' in the output file at the
       end of processing all the command line arguments if
       it finds GTID_NEXT is in invalid state.

       After this patch, if you are merging two or more
       binary log files, you will see two differences in
       the output when compared to the before the patch

       a) When mysqlbinlog start processing the second
          binary log file, if required (i.e., if the 
          previous binary log left gtid_next in a invalid
          state), it generates SET GTID_NEXT=AUTOMATIC.
       b) Before the patch, mysqlbinlog outputs session
          variable information for every binary log.
          Now that we will have only one print_event_info
          per run, this session variables value will be
          printed only once *unless there is a change*.
          Example of session variables:
            SET @@session.pseudo_thread_id=999999999/*!*/;
            SET @@session.foreign_key_checks=1
            SET @@session.sql_mode=1073741824/*!*/;
            SET @@session.auto_increment_increment=1,
            SET @@session.auto_increment_offset=1/*!*/;
            SET @@session.lc_time_names=0/*!*/;
            SET @@session.collation_database=DEFAULT/*!*/;