[1.2.X] Fixed #13613 -- Ensure that forms.URLField and forms.EmailField are...

[1.2.X] Fixed #13613 -- Ensure that forms.URLField and forms.EmailField are used on a modelform. This ensures that fields are URL and Email fields are cleaned consistently when included on model forms. Thanks to amadison for the report.

Backport of r13475 from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.2.X@13476 bcc190cf-cafb-0310-a4f2-bffc1f526a37