Allow CsrfResponseMiddleware to be used if templates cannot be updated.

For the case where someone is using contrib views with custom templates that
they cannot update to use the template tag, it should be possible to use
CsrfResponseMiddleware.  This requires that 'csrf_response_exempt' is not
used for the admin views.



git-svn-id: http://code.djangoproject.com/svn/django/trunk@11683 bcc190cf-cafb-0310-a4f2-bffc1f526a37