Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

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

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

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

/* -> /*- for copyright notices, minor format tweaks as necessary

Add a generic implementation of inittodr() and resettodr(), as well as
a set of helper routines to deal with real-time clocks. The generic
functions access the clock diver using a kobj interface. This is intended
to reduce code reduplication and make it easy to support more than one
clock model on a single architecture.

This code is currently only used on sparc64, but it is planned to convert
the code of the other architectures to it later.