Ability to disable creation of MyISAM tables

We use MariaDB exclusively in Galera clusters. We do not enable MyISAM replication because it is not recommended.

We wish there were a way to prevent users from creating MyISAM tables, since there is no way to raise a warning that such tables are not replicated.

This is especially useful given that we've found a way for users to crash MariaDB if they have the ability to create/access MyISAM tables. This is the result of our investigation into CVE-2015-3210.

This is evidently possible, since there is a community provided plugin. We do not plan to use this plugin, as it is not intended for MariaDB.