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.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@13475 bcc190cf-cafb-0310-a4f2-bffc1f526a37