Fixed #17011 - Made override_settings modify a decorated class in-place rather...

Fixed #17011 - Made override_settings modify a decorated class in-place rather than creating a dynamic subclass, so as to avoid infinite recursion when used with super(). Thanks jsdalton for the report and patch.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@16942 bcc190cf-cafb-0310-a4f2-bffc1f526a37