Fixed #14749 -- added support for using Django's file object as context...

Fixed #14749 -- added support for using Django's file object as context managers.  Thanks to Florian Apolloner for the patch.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@14671 bcc190cf-cafb-0310-a4f2-bffc1f526a37