add setOnMessageCallback with r-value

ixwebsocket/IXWebSocketMessageQueue.cpp

@@ -76,6 +76,11 @@ namespace ix
     {
         _onMessageUserCallback = callback;
     }
+
+    void WebSocketMessageQueue::setOnMessageCallback(OnMessageCallback&& callback)
+    {
+        _onMessageUserCallback = std::move(callback);
+    }
     
     WebSocketMessageQueue::MessagePtr WebSocketMessageQueue::popMessage()
     {

ixwebsocket/IXWebSocketMessageQueue.h

@@ -25,6 +25,7 @@ namespace ix
         void bindWebsocket(WebSocket* websocket);
 
         void setOnMessageCallback(const OnMessageCallback& callback);
+        void setOnMessageCallback(OnMessageCallback&& callback);
 
         void poll(int count = 512);