wined3d: Make fullscreen windows use HWND_TOPMOST instead of HWND_TOP.

dlls/wined3d/device.c

@@ -1032,7 +1032,7 @@ void CDECL wined3d_device_setup_fullscreen_window(struct wined3d_device *device,
 
     SetWindowLongW(window, GWL_STYLE, style);
     SetWindowLongW(window, GWL_EXSTYLE, exstyle);
-    SetWindowPos(window, HWND_TOP, 0, 0, w, h, SWP_FRAMECHANGED | SWP_SHOWWINDOW | SWP_NOACTIVATE);
+    SetWindowPos(window, HWND_TOPMOST, 0, 0, w, h, SWP_FRAMECHANGED | SWP_SHOWWINDOW | SWP_NOACTIVATE);
 
     device->filter_messages = filter_messages;
 }