Merge r992625 from trunk:

mod_cache: Check the request to determine whether we are allowed
to return cached content at all, and respect a "Cache-Control:
no-cache" header from a client. Previously, "no-cache" would
behave like "max-age=0".

Submitted by: minfrin
Reviewed by: minfrin, jim, covener


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@1053600 13f79535-47bb-0310-9956-ffa450edef68