Add a test case for corrupting SYS_TABLES.TYPE,
and for ROW_FORMAT=REDUNDANT, the unused field SYS_TABLES.MIX_LEN
that must be ignored (InnoDB before MySQL 5.5 wrote uninitialized
garbage to this column).

MariaDB 10.0 appears to validate the SYS_TABLES.TYPE properly.
This is a test-only change.