[1.0.X] Final pieces (he says, hopefully) of r9945 changes.

Fixed "django-admin.py diffsettings" and some GeoDjango stuff.
Refs #10395.

Backport of r9960 and r9961 from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.0.X@9962 bcc190cf-cafb-0310-a4f2-bffc1f526a37