[1.1.X] Fixed #11353 -- `GeometryProxy` descriptor no longer chokes when...

[1.1.X] Fixed #11353 -- `GeometryProxy` descriptor no longer chokes when accessed from a class rather than an instance, thanks yml and Tobu; removed unnecessary imports from `types` and cleaned up whitespace.

Backport of r12584 from trunk.


git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.1.X@12585 bcc190cf-cafb-0310-a4f2-bffc1f526a37