WL#9457: Deprecate support for non-native partitioning

Affects: Server-5.7   —   Status: Complete

Support for non-native partitioning has been removed in 8.0. This feature must
be deprecated in 5.7.

User Documentation
==================

* http://dev.mysql.com/doc/refman/5.7/en/server-options.html#option_mysqld_disable-partition-engine-check
* http://dev.mysql.com/doc/refman/5.7/en/partitioning.html (initial note)