[PATCH 5/5] user32: Implement better stub of OpenInputDesktop.

[Vincent Povirk]

I don't think it's possible to properly implement SwitchDesktop in
either the X11 or Mac driver. There's just nothing sensible for it to
do.

One possible strategy would be to implement SwitchDesktop in user32
and wineserver. Wineserver could logically track the input desktop,
and OpenInputDesktop would return the "correct" desktop, but
SwitchDesktop wouldn't really do anything. If in the future we decide
there's something SwitchDesktop can do that makes sense, we can add a
function for it to the user driver, and OpenInputDesktop probably
won't need to change.