Switch to indicate ebook mode

[Dan Williams]

I can't remember if I ever got a straight answer on this.  Is there a
switch somewhere that we can access that indicates whether or not the
laptop has been swiveled into ebook mode?

Ideally, the switch would generate an interrupt which we could receive
and automatically rotate the X display and switch to B&W mode when the
keyboard is hidden [1].  It's not a great experience to have to expose a
toggle somewhere if we can't figure out when we're in ebook mode,
especially if we had to rely on activities to provide that toggle in
their own UI.

Dan

[1] and possibly provide an API for games and such to block the switch.
But we should switch by default, _not_ require people to find something
in the UI to do it.