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

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

Add /dev/speaker support to amd64.

The following repo-copies were made (by Mark Murray):

sys/i386/isa/spkr.c -> sys/dev/speaker/spkr.c
sys/i386/include/speaker.h -> sys/dev/speaker/speaker.h
share/man/man4/man4.i386/spkr.4 -> share/man/man4/spkr.4

'speaker' not 'atspeaker'

Retire 'atspeaker' and 'pcspeaker'. We'll use 'speaker' which
is the same as the config device directive.

Reminded by: Takahashi Yoshihiro <nyan@jp.FreeBSD.org>