Communication: Atomic sync messages

If waitForMessageSync() is called in two threads for the same message
the callback for both will be invoked with the first send.

include/icsneo/communication/communication.h

@@ -88,6 +88,7 @@ protected:
 	std::atomic<bool> redirectingRead{false};
 	std::function<void(std::vector<uint8_t>&&)> redirectionFn;
 	std::mutex redirectingReadMutex; // Don't allow read to be disabled while in the redirectionFn
+	std::mutex syncMessageMutex;
 
 	void dispatchMessage(const std::shared_ptr<Message>& msg);
 	void handleInput(Packetizer& p, std::vector<uint8_t>& readBytes);