Fix flickering window on move

Using this method perform very minor flicker when moving around on screen.

src/Cxbx/WndMain.cpp

@@ -1301,8 +1301,7 @@ LRESULT CALLBACK WndMain::WndProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lP
 		{
 			// Redraw the window on move, prevents corrupt background image that happens
 			// when windows doesn't call the WM_DRAW event when the window is moved too quickly.
-			InvalidateRect(NULL, NULL, false);
-			UpdateWindow(hwnd);
+			RedrawWindow(hwnd, NULL, NULL, RDW_INVALIDATE);
 			break;
 		}