Fixed #13304 -- Updated auth decorators so they can be used with callable...

Fixed #13304 -- Updated auth decorators so they can be used with callable classes. Thanks to Horst Gutmann for the report and patch.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@12938 bcc190cf-cafb-0310-a4f2-bffc1f526a37