Merge r1726881, r1727111 from trunk:

* Introduce SSLOCSPProxyURL in order to do OCSP requests via a HTTP proxy.
  Documentation to follow.


* Change entry and documentation for SSLOCSPProxyURL
Submitted by: rpluem
Reviewed/backported by: jim


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1733066 13f79535-47bb-0310-9956-ffa450edef68