maximized state and normal frame size lost after hide/show

[Cosmin Apreutesei]

> I'll try XUnmapWindow() and send UnmapNotify myself like Qt does, see how that goes.

Doesn't work. Looks like XWithdrawWindow() is just XUnmapWindow() +
XSendEvent(XUnmapEvent) after all.

Well, at least it was an opportunity to see how much the advice of
using Qt is worth :)

And btw, about the flakiness of waiting on events to simulate blocking
behavior, note that unmapping a minimized window doesn't get you a
UnmapNotify event back since the window is already technically
unmapped. I'll try changing _NET_WM_HIDDEN next to see where this gets
me (even though my gut tells me some WMs would have a hard time
respecting this obscurity as google already suggests[1]).

[1] http://marc.info/?l=kwin&m=135777696125403&w=2