Fixed #14156 -- Modified the way CSRF protection is applied to flatpages so...

Fixed #14156 -- Modified the way CSRF protection is applied to flatpages so that the flatpage middleware doesn't cause all POSTs resulting in 404s to turn into 403s. Thanks to patrys for the report.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@13641 bcc190cf-cafb-0310-a4f2-bffc1f526a37