Added and tested the network queue in the server

This is a reimplementation of the old network queue, but using a class.
This still uses a separate thread, so that packets can wait if there's any
lag. Really, thinking about it, I wonder how necessary this was.

On the upside, no singletons this time. Which means that you can have
several instances of UDPNetworkManager. That's unintentional, but good to
know.

server/network_queue.hpp

@@ -0,0 +1,35 @@
+#ifndef NETWORKQUEUE_HPP_
+#define NETWORKQUEUE_HPP_
+
+#include "udp_network_utility.hpp"
+#include "network_packet.hpp"
+
+#include "SDL/SDL_thread.h"
+
+#include <deque>
+
+class NetworkQueue {
+public:
+	NetworkQueue() = default;
+	~NetworkQueue() = default;
+
+	void Init(UDPNetworkUtility*);
+	void Quit();
+	void Kill();
+
+	NetworkPacket Peek();
+	NetworkPacket Pop();
+	void Flush();
+private:
+	friend int networkQueueThread(void*);
+	void ResetMembers();
+
+	bool running = false;
+
+	UDPNetworkUtility* netUtil = nullptr;
+	SDL_sem* lock = nullptr;
+	SDL_Thread* thread = nullptr;
+	std::deque<NetworkPacket> queue;
+};
+
+#endif