Merge r541926, r541990 from trunk:

PR#39710 - badly broken errordocuments for CGI

We've just had another duplicate report of this on bugzilla.
We've got a simple patch, and people asking WTF is going on
with inaction.  Noone seems clear on why the patch shouldn't
be applied (http://marc.info/?l=apache-httpd-dev&m=117760311129386&w=2).


* Prevent running through the error stack by returning OK and setting r->status
  accordingly if ret is HTTP_NOT_MODIFIED as this breaks mod_cache validating a
  stale entity.

Reviewed by: jim


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@556973 13f79535-47bb-0310-9956-ffa450edef68