Merge r636386, r636653 from trunk:

* Restore the original request headers if the cached resource was stale, as they
  may be needed by further output filters like the byterange filter to make the
  correct decisions.

PR: 44579


* Do not do Range requests if we use our own conditionals for validating
  a cache entity: If we get 304 the Range does not matter and otherwise the
  entity changed and we want to have the complete entity.

PR: 44579

Submitted by: rpluem
Reviewed by: jim


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@660584 13f79535-47bb-0310-9956-ffa450edef68