Revision 1890605

  *) core/mod_proxy/mod_ssl:
     Adding `outgoing` flag to conn_rec, indicating a connection is
     initiated by the server to somewhere, in contrast to incoming
     connections from clients.
     Adding 'ap_ssl_bind_outgoing()` function that marks a connection
     as outgoing and is used by mod_proxy instead of the previous
     optional function `ssl_engine_set`. This enables other SSL
     module to secure proxy connections.
     The optional functions `ssl_engine_set`, `ssl_engine_disable` and
     `ssl_proxy_enable` are now provided by the core to have backward
     compatibility with non-httpd modules that might use them. mod_ssl
     itself no longer registers these functions, but keeps them in its
     header for backward compatibility.
     The core provided optional function wrap any registered function
     like it was done for `ssl_is_ssl`.