Fixed #15299 -- Started the process of migrating the auth context processor...

Fixed #15299 -- Started the process of migrating the auth context processor support classes into the auth context processor module. Thanks to shailesh for the report, and v1v3kn for the draft patch.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@15635 bcc190cf-cafb-0310-a4f2-bffc1f526a37