winex11.drv: Use a separate virtual desktop display device handler.
If we want to query host monitor dimensions, we need to use XRandR
or Xinerama handler. However when in virtual desktop mode, its display
device handler overrides other handlers. So we need to separate them.
Then we can implement features that require host monitor dimensions like
checking whether the virtual desktop window is fullscreen.
Signed-off-by: Zhiyi Zhang <zzhang@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>