Use ffmpeg for Windows Video Dumping instead of VFW

Source/Core/VideoCommon/AVIDump.h

@@ -25,11 +25,7 @@ private:
 	static void* GetFrame();
 
 public:
-#ifdef _WIN32
-	static bool Start(HWND hWnd, int w, int h);
-#else
 	static bool Start(int w, int h);
-#endif
 	static void AddFrame(const u8* data, int width, int height);
 	static void Stop();
 	static void DoState();