Fixed #1579 - added support for 'Q' objects in limit_choices_to.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@2850 bcc190cf-cafb-0310-a4f2-bffc1f526a37

docs/model-api.txt

@@ -704,6 +704,10 @@ relationship should work. All are optional:
                              ``pub_date`` before the current date/time to be
                              chosen.
 
+                             Instead of a dictionary this can also be a ``Q`` object
+                             (an object with a ``get_sql()`` method) for more complex
+                             queries.
+
                              Not compatible with ``edit_inline``.
 
     ``max_num_in_admin``     For inline-edited objects, this is the maximum