Merge r620133, r724515, r724805, r725077, r952828 from trunk:

Sub-requests are created and used with two purposes; sometimes
simply to 'see' what a request would do; as to fill out an SSI,
validate access or similar - and is then discarded. And sometimes
as the precursor to becoming the actual request; e.g. when mod_dir
checks if an /index.html can be served for a '/'.

In the latter case it is important to preserve the output filters
'for real'; whereas in the first case they have to be reset to
purely the minimal proto filters (if at all). This patch instates
the output filters in 3 cases where sub-requests are/may in fact
be used as the real request later on.

This is a relatively risky change (which should not be back-ported 
without further discussion) and may break caches in combination 
with internal redirects/vary/negotiation in subtle ways.

See the thread starting at [1] and in particular the general 
concerns of rpluem at [2] with respect to sub requests 
and (fast_)internal redirects possibly needing a more 
thorough overhaul.

1: http://mail-archives.apache.org/mod_mbox/httpd-dev/200802.mbox/ajax/%3c335D1A4B-25E2-4FF1-8CDF-5010A7FBD293@webweaving.org%3e
2: http://mail-archives.apache.org/mod_mbox/httpd-dev/200802.mbox/%3c47ACE1D4.4060702@apache.org%3e



* Correctly remove the SUBREQ_CORE filter from the filter chain if we do an
  internal fast redirect and if the new redirected request is NO subrequest.
  This fixes at least one of the possible subtle issues mentioned in the
  comment to r620133.


reset chain if we need to...


Hopefully the final fix for the subreq/filter issue. The
prob was that we at this point could still have some
stale and incorrect refs when we adjusted the f-stack.
So move the update earlier so when we adjust, we're
affecting r. Ruediger and Jim pretty much
simultaneously :)


* modules/http/http_request.c (internal_internal_redirect): For a
  subrequest, preserve any filters in the output filter chain which
  were not specific to the subrequest across the redirect (where
  f->r does not point to the subreq's request_rec).

PR: 17629, 43939

Reviewed by: rpluem, jim, niq


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@988400 13f79535-47bb-0310-9956-ffa450edef68