Run graphics rendering on a dedicated thread.

The main game thread can offload some of the CPU cost to the rendering thread, freeing up its time to run more logic and render ticks.

OpenRA.Game/Graphics/PlatformInterfaces.cs

@@ -17,7 +17,7 @@ namespace OpenRA
 {
 	public interface IPlatform
 	{
-		IGraphicsDevice CreateGraphics(Size size, WindowMode windowMode);
+		IGraphicsDevice CreateGraphics(Size size, WindowMode windowMode, int batchSize);
 		ISoundEngine CreateSound(string device);
 	}