fix window origin in pseudofullscreen

OpenRA.Gl/GraphicsDevice.cs

@@ -68,6 +68,7 @@ namespace OpenRA.GlRenderer
 			case WindowMode.PseudoFullscreen:
 				// pseudo-fullscreen only reliably works on windows; fall back to fullscreen for everyone else
 				windowFlags |= ( Environment.OSVersion.Platform == PlatformID.Win32NT ) ? Sdl.SDL_NOFRAME : Sdl.SDL_FULLSCREEN;
+				Environment.SetEnvironmentVariable( "SDL_VIDEO_WINDOW_POS", "0,0" );
 				break;
 			default:
 				break;