The parameter innodb_idle_flush_pct that was introduced in
MariaDB Server 10.1.2 by MDEV-6932 has no effect ever since
the InnoDB changes from MySQL 5.7.9 were applied in
commit 2e814d4702.
Let us declare the parameter as MARIADB_REMOVED_OPTION.
For earlier versions, commit ea9cd97f85
declared the parameter deprecated.
We will default to MUTEXTYPE=sys (using OSTrackMutex) for those
ib_mutex_t that have not been replaced yet.
The view INFORMATION_SCHEMA.INNODB_SYS_SEMAPHORE_WAITS is removed.
The parameter innodb_sync_array_size is removed.
FIXME: innodb_fatal_semaphore_wait_threshold will no longer be enforced.
We should enforce it for lock_sys.mutex and dict_sys.mutex somehow!
innodb_sync_debug=ON might still cover ib_mutex_t.
