BACKWARDS-INCOMPATIBLE CHANGE: Removed SetRemoteAddrFromForwardedFor middleware.

In a nutshell, it's been demonstrated that this middleware can never be made reliable enough for general-purpose use, and that (despite documentation to the contrary) its inclusion in Django may lead application developers to assume that the value of ``REMOTE_ADDR`` is "safe" or in some way reliable as a source of authentication. So it's gone.

See the Django 1.1 release notes for full details, as well as upgrade instructions.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@11363 bcc190cf-cafb-0310-a4f2-bffc1f526a37