Prevent "core" namespace removal

(cherry picked from commit f8cde2e1eddfb2fe341a494518766e1288739d2c)
Remove all dependency on mysql extension

The mysql extension is deprecated in PHP 5.5

(cherry picked from commit ffbf2be2b979f40fb8d4aea6f70fbca14e751bcc)

Conflicts:
	core/docs/changelog.txt