Fixed #16198 -- Ported the model_forms doctests. Our long national nightmare is over. Oh, and we have always been at war with doctests. Thanks to Peter van Kampen and Gregor Müllegger for the patch.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@16358 bcc190cf-cafb-0310-a4f2-bffc1f526a37