Fixed lp:925377 "Querying myisam table metadata while 'alter table..enable keys' is running may corrupt the table"
Fixed wrong mutex order bug in Aria when flush_log_for_bitmap() was called when table is not yet marked for change.

include/my_base.h:
  Added flag that table is opened only for status
mysql-test/r/myisam-big.result:
  Test case for lp:925377
mysql-test/t/myisam-big.test:
  Test case for lp:925377
sql/sql_base.cc:
  If thd->version == 0 (happens only when we are opening a table that is flushed under  MYSQL_LOCK_IGNORE_FLUSH), open the table in HA_OPEN_FOR_STATUS mode
storage/maria/ma_bitmap.c:
  Fixed wrong mutex order bug in Aria when flush_log_for_bitmap() was called when table is not yet marked for change.
storage/maria/ma_dbug.c:
  Ignore last_version <= 1 as these are either flushed or only opened for status
storage/maria/ma_open.c:
  Use last_version=1 as a marker that table was opened with HA_OPEN_FOR_STATUS.
  In this case we just open a new version of the table in read only mode.
storage/myisam/mi_create.c:
  Update prototype
storage/myisam/mi_dbug.c:
  Ignore last_version <= 1 as these are either flushed or only opened for status
storage/myisam/mi_open.c:
  Use last_version=1 as a marker that table was opened with HA_OPEN_FOR_STATUS.
  If HA_OPEN_FOR_STATUS is used, we will not assert if there is an old not-to-be-used version of the table existing.
  In this case we just open a new version of the table in read only mode.
storage/myisam/myisamdef.h:
  Updated prototype