Support MySQL 5.7.5's deprecation of EOF packet

[Abscissa]

Well this is annoying...

According to protocol spec, the EOF packet (which mysql-native uses) is deprecated as of MySQL 5.7.5, replaced by enhancements to the OK packet as of MySQL 5.7.

Need to test that (this looks helpful, esp the comment from Aug 12) and handle it.

Also should find out MariaDB's take on all of this.