Revert "Merge branch 'Dimon4eg-message-queue'"

This reverts commit 13fa325134, reversing
changes made to aecd5e9c94.

ixwebsocket/IXWebSocket.h

@@ -119,11 +119,7 @@ namespace ix
         void close(uint16_t code = 1000,
                    const std::string& reason = "Normal closure");
 
-        // Set callback to receive websocket messages.
-        // Be aware: your callback will be executed from websocket's internal thread!
-        // To receive message events in your thread, look at WebSocketMessageQueue class
         void setOnMessageCallback(const OnMessageCallback& callback);
-
         static void setTrafficTrackerCallback(const OnTrafficTrackerCallback& callback);
         static void resetTrafficTrackerCallback();