Backport of r760866:

* Add SSLProxyCheckPeerExpire and SSLProxyCheckPeerCN directives to enable
  stricter checking of remote server certificates.

  (docs/manual/mod/mod_ssl.xml)
    Documentation of SSLProxyCheckPeerExpire and SSLProxyCheckPeerCN.

  (modules/proxy/mod_proxy_http.c)
    Set the hostname of the request URL as note on the connection.

  (modules/ssl/ssl_private.h)
    Add proxy_ssl_check_peer_expire and proxy_ssl_check_peer_cn fields to
    the SSLSrvConfigRec.

  (modules/ssl/ssl_engine_config.c)
    Directives stuff for SSLProxyCheckPeerExpire and SSLProxyCheckPeerCN.

  (modules/ssl/ssl_engine_io.c)
    Check whether the remote servers certificate is expired / if there is a
    mismatch between the requested hostanme and the remote server certificates
    CN field.
    Be able to parse ASN1 times.

  (modules/ssl/mod_ssl.c)
    Directives stuff for SSLProxyCheckPeerExpire and SSLProxyCheckPeerCN.

Submitted by: rpluem
Reviewed by: rpluem, jim, jfclere


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@768504 13f79535-47bb-0310-9956-ffa450edef68