Merge r1587607, r1588868 from trunk:

Merge r1587607, r1588868 from trunk:

mod_ssl: Add hooks to allow other modules to perform processing at
several stages of initialization and connection handling.  See
mod_ssl_openssl.h.

This is enough to allow implementation of Certificate Transparency
outside of mod_ssl.

Initialize post_handshake_rc for case where a failure has
already occurred (doesn't change execution but avoids warning
with some levels of gcc).

Pointed out by: kbrand

Submitted by: trawick
Reviewed/backported by: jim

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1735886 13f79535-47bb-0310-9956-ffa450edef68