Observe WAL for the table's state: all log records needed for undoing
uncommitted state must be in the log before we flush state.


storage/maria/ha_maria.cc:
  comments
storage/maria/ma_bitmap.c:
  Comment for why there is no bug
storage/maria/ma_blockrec.c:
  comment for why there is no bug
storage/maria/ma_checkpoint.c:
  Observe WAL for the table's state: all log records needed for undoing
  uncommitted state must be in the log before we flush state. I tested
  by hand that the bug existed (create table, insert one row into it
  but let that insert pause after increasing data_file_length, let
  checkpoint start but kill it after it has flushed state).
  Log contains nothing, table is not recovered though it has
  a too big data_file_length. With this bugfix, the log contains
  REDO so table is opened so data_file_length is corrected.
storage/maria/ma_close.c:
  If table is read-only we must never write to it.
  Should be a no-change in fact, as if read-only, share->changed is
  normally always false.
storage/maria/ma_recovery.c:
  documenting bug found by Monty. Print when fixing data_file_length.