Fixed #12427 -- Started the deprecation path for cmemcache support. Thanks to...

Fixed #12427 -- Started the deprecation path for cmemcache support. Thanks to otherjacob for his work on this issue.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@12754 bcc190cf-cafb-0310-a4f2-bffc1f526a37