3rdparty: add MultiEmulator by 2010kohtep

* patched to be portable, turned into a static library
* integrated to the engine

3rdparty/MultiEmulator/src/OldRevEmu.cpp

@@ -0,0 +1,13 @@
+#include "multi_emulator.h"
+
+int GenerateOldRevEmu(void* pDest, int nSteamID)
+{
+	auto pTicket = (int*)pDest;
+	auto pbTicket = (unsigned char*)pDest;
+
+	pTicket[0] = 0xFFFF;                       // +0, header
+	pTicket[1] = (nSteamID ^ 0xC9710266) << 1; // +4, SteamId
+	*(short *)&pbTicket[8] = 0;                // +8, unknown, in original emulator must be 0
+
+	return 10;
+}