Fixed #7098 -- Old-style related-model order_by() syntax was being incorrectly

marked as erroneous. It's just more dangerous and risky, not forbidden. This
commit restores backwards compatibility there.


git-svn-id: http://code.djangoproject.com/svn/django/trunk@7490 bcc190cf-cafb-0310-a4f2-bffc1f526a37