[1.2.X] Fixed #14199 -- Added a missing table creation statement in the db...

[1.2.X] Fixed #14199 -- Added a missing table creation statement in the db cache backend cull implementation, and added tests for cache culling. Thanks to Tim for the report.

Backport of r13678 from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.2.X@13679 bcc190cf-cafb-0310-a4f2-bffc1f526a37