* recovery from ha_maria now skips replaying DDLs (too dangerous)
* maria_read_log still replays DDLs, print warning about issues
* fixes to replaying of REDO_RENAME
* don't replay DDLs on corrupted tables (safer)
* print a one-line message when really doing a recovery (applies to
ha_maria, not maria_read_log) i.e. some REDOs or UNDOs are read.


storage/maria/ma_checkpoint.c:
  fix for assertion failure
storage/maria/ma_recovery.c:
  * Recovery from ha_maria now skips replaying DDLs (as the initial
  plan said) as this is unsafe in case of crashes during the DDL;
  applying the records may do harm (destroy important files)
  so we prefer to leave the "mess" of files untouched. A proper
  recovery of DDLs requires very careful thinking, probably testing
  separately the existence of the data and index file instead of
  using maria_open() which tests the existence of both, and maybe
  storing create_rename_lsn in the data file too.
  * maria_read_log still replays DDLs, we print a warning about dangers
  (due to ALTER TABLE not logging insertions into the tmp table; we
  will maybe need an option to have logging of those insertions).
  * fixes to replaying of REDO_RENAME (test create_rename_lsn of 'new_name'
  table if it exists; if that table exists and is more recent than the
  record, remove the 'old_name' table).
  * don't replay DDLs on corrupted tables (play safe)
  * fail also in non-debug builds if table is open when it should not be
  (when creating it for example, it should not be already open).
  * when the trace file is not stdout (i.e. when this is ha_maria),
  if really doing a recovery (reading REDOs or UNDOs), print a one-line
  message to stderr to inform about start and end of recovery
  (useful to know what mysqld is doing, especially if it takes long
  or crashes).
storage/maria/ma_recovery.h:
  parameter to replay DDLs or not
storage/maria/maria_read_log.c:
  replay DDLs in maria_read_log, to be able to recreate tables from
  scratch.