Support for OpenSSL 1.1.0:

- partial support for renegotiations.
  - Not a good design, need to poll until
    renegotitation has finished.
  - Loop criterion not right, if no client certs
    will be send.
  - Also doesn't work for EC or DH ciphers.
    Unclear how to fix with current 1.1.0
    API.
  - Details see
    http://marc.info/?t=145493359200002&r=1&w=2

Backport of r1729341 from trunk.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x-openssl-1.1.0-compat@1755821 13f79535-47bb-0310-9956-ffa450edef68