[1.0.X]: Fixed #8140 -- Made `UserManager.create_superuser` return the new...

[1.0.X]: Fixed #8140 -- Made `UserManager.create_superuser` return the new `User` object, based on patch from ericholscher.

Backport of r10217 from trunk.


git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.0.X@10218 bcc190cf-cafb-0310-a4f2-bffc1f526a37