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

- Move timerreg.h to <arch>/include and split i8253 specific defines into
i8253reg.h, and add some defines to control a speaker.
- Move PPI related defines from i386/isa/spkr.c into ppireg.h and use them.
- Move IO_{PPI,TIMER} defines into ppireg.h and timerreg.h respectively.
- Use isa/isareg.h rather than <arch>/isa/isa.h.

Tested on: i386, pc98