Introducing websocket support in router and libunit.

src/nxt_unit_request.h

@@ -20,6 +20,7 @@ struct nxt_unit_request_s {
     uint8_t               remote_length;
     uint8_t               local_length;
     uint8_t               tls;
+    uint8_t               websocket_handshake;
     uint32_t              server_name_length;
     uint32_t              target_length;
     uint32_t              path_length;