merge r1703952 from trunk

Support compilation against libssl built with OPENSSL_NO_SSL3,
and change the compiled-in default for SSL[Proxy]Protocol to "all -SSLv3",
in accordance with RFC 7568. PR 58349, PR 57120.

Proposed by: kbrand
Reviewed by: ylavic, jorton


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1706008 13f79535-47bb-0310-9956-ffa450edef68