Fixed #14235 - UnicodeDecodeError in CSRF middleware

Thanks to jbg for the report.

This changeset essentially backs out [13698] in favour of a method that
sanitizes the token rather than escaping it.



git-svn-id: http://code.djangoproject.com/svn/django/trunk@13732 bcc190cf-cafb-0310-a4f2-bffc1f526a37