[libxkbcommon] Pull request - many changes

[wettstein509 at solnet.ch]

> And the changed you made are much better; especially removing geometry
> (by far the ugliest part) and overlays and radio groups (what the hell
> are those again?). Also removing atoms from the public API.

Overlays are a very useful feature (I do not say this theoretically, I
actually do use them).  I would regret it very much if they would not be
supported anymore.  As I do not know what libxkbcommon is used for, I
wonder what will be the consequences of this removal?  Do I have to
worry about the future of this beloved XKB feature?

Andreas