Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Clean up the mac GPIO interface a little. Also remove bogus copyright
and 3rd license clause.

Submitted by: Marco Trillo

Add ADB support. This provides support for the external ADB bus on the PowerMac
G3 as well as the internal ADB keyboard and mice in PowerBooks and iBooks. This
also brings in Mac GPIO support, for which we should eventually have a better
interface.

Obtained from: NetBSD (CUDA and PMU drivers)