[1.3.X] Fixed #14648 -- Fixed annotated date querysets when `GeoManager` is...

[1.3.X] Fixed #14648 -- Fixed annotated date querysets when `GeoManager` is used.  Thanks, codysoyland, for the bug report.

Backport of r16796 from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.3.X@16844 bcc190cf-cafb-0310-a4f2-bffc1f526a37