Remove support for the X-Forwarded-For header.
Remove support for the X-Forwarded-For header.

Follow the tracks of Django where it was removed in version 1.1. The
reasons and a workaround are described here:
https://docs.djangoproject.com/en/dev/releases/1.1/#removed-setremoteaddrfromforwardedfor-middleware

Fix #338.

ivelum/django-debug-toolbar,tim-schilling/django-debug-toolbar,calvinpy/django-debug-toolbar,stored/django-debug-toolbar,peap/django-debug-toolbar,jazzband/django-debug-toolbar,guilhermetavares/django-debug-toolbar,Endika/django-debug-toolbar,calvinpy/django-debug-toolbar,django-debug-toolbar/django-debug-toolbar,calvinpy/django-debug-toolbar,ivelum/django-debug-toolbar,spookylukey/django-debug-toolbar,django-debug-toolbar/django-debug-toolbar,sidja/django-debug-toolbar,Endika/django-debug-toolbar,pevzi/django-debug-toolbar,django-debug-toolbar/django-debug-toolbar,seperman/django-debug-toolbar,seperman/django-debug-toolbar,peap/django-debug-toolbar,ivelum/django-debug-toolbar,ChristosChristofidis/django-debug-toolbar,Endika/django-debug-toolbar,tim-schilling/django-debug-toolbar,jazzband/django-debug-toolbar,barseghyanartur/django-debug-toolbar,megcunningham/django-debug-toolbar,jazzband/django-debug-toolbar,spookylukey/django-debug-toolbar,seperman/django-debug-toolbar,guilhermetavares/django-debug-toolbar,guilhermetavares/django-debug-toolbar,peap/django-debug-toolbar,barseghyanartur/django-debug-toolbar,barseghyanartur/django-debug-toolbar,ChristosChristofidis/django-debug-toolbar,spookylukey/django-debug-toolbar,stored/django-debug-toolbar,pevzi/django-debug-toolbar,tim-schilling/django-debug-toolbar,megcunningham/django-debug-toolbar,sidja/django-debug-toolbar,pevzi/django-debug-toolbar,megcunningham/django-debug-toolbar,sidja/django-debug-toolbar,stored/django-debug-toolbar,ChristosChristofidis/django-debug-toolbar