* Correct ConfigureNotify events sent to fullscreen windows.
* Exit fullscreen mode before switching workspace.
* Temporarily treat `xcb:Atom:_NET_WM_STATE_ABOVE` as
`xcb:Atom:_NET_WM_STATE_FULLSCREEN` since
a) "plugin-container" (Flash Player) seems only set this, and
b) it's not normally used by applications.
This makes fullscreen videos working in e.g. iceweasel.