The bug was that if you have two TL_WRITE_DELAYED at the same time,
mi_lock_databases() could be done in the wrong order and we could write the wrong header to the MyISAM index file.


sql/mysql_priv.h:
  Fix bug in insert delayed with prepared statements
sql/sql_base.cc:
  Fix bug in insert delayed with prepared statements
sql/sql_prepare.cc:
  Fix bug in insert delayed with prepared statements
  The bug was that if you have two TL_WRITE_DELAYED at the same time,
  mi_lock_databases() could be done in the wrong order and we could write the wrong header to the MyISAM index file.