Stream: client SSL certificates verification support. New directives: "ssl_verify_client", "ssl_verify_depth", "ssl_client_certificate", "ssl_trusted_certificate", and "ssl_crl". New variables: $ssl_client_cert, $ssl_client_raw_cert, $ssl_client_s_dn, $ssl_client_i_dn, $ssl_client_serial, $ssl_client_fingerprint, $ssl_client_verify, $ssl_client_v_start, $ssl_client_v_end, and $ssl_client_v_remain.