Merged /httpd/httpd/trunk:r1851621,1852128,1862075

Merged /httpd/httpd/trunk:r1851621,1852128,1862075

  *) mod_ssl/mod_md: reversing dependency by letting mod_ssl offer hooks for
     adding certificates and keys to a virtual host. An additional hook allows
     answering special TLS connections as used in ACME challenges.
     Adding 2 new hooks for init/get of OCSP stapling status information when
     other modules want to provide those. Falls back to own implementation with
     same behaviour as before.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1863988 13f79535-47bb-0310-9956-ffa450edef68