Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.Approved by: re (implicit)Sponsored by: The FreeBSD Foundation
Update @freebsd.org email addresses to @FreeBSD.org as is theprecedent.
$Id$ -> $FreeBSD$
add missing cvs Id lines.
Add a zero(4) man page to describe /dev/zero. Update null(4) to xrefthis new man page.