Fixed #12245 -- Corrected target app handling for auto-generated m2m models...

Fixed #12245 -- Corrected target app handling for auto-generated m2m models when the parent model isn't in the models module (or a subpackage thereof). Thanks to emulbreh for the report and patch.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@11755 bcc190cf-cafb-0310-a4f2-bffc1f526a37