Fixing automerge problem and updating comments referring to exec_event().


mysql-test/r/rpl_incident.result:
  Result change
sql/log_event.cc:
  Renaming exec_event() to do_apply_event().
sql/log_event.h:
  Renaming exec_event() to do_apply_event().
sql/rpl_rli.cc:
  Fixing comments referring to exec_event(), which does not exist any more.
sql/sql_class.h:
  Fixing comments referring to exec_event(), which does not exist any more.