Added some tests to modeltests/many_to_one that demonstrate a...

Added some tests to modeltests/many_to_one that demonstrate a post-queryset-refactor bug in dates(). Refs #7097

git-svn-id: http://code.djangoproject.com/svn/django/trunk@7485 bcc190cf-cafb-0310-a4f2-bffc1f526a37