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

Revert most part of 200420 as requested, as more review and polish is
needed.

Remove unneeded header includes from usr.bin/ except contributed code.

Tested with: make universe

Import ar(1) front-end. (aka 'BSD' ar)

Reviewed by: jkoshy
Approved by: jkoshy (mentor)
Tested by: erwin (ports build test on pointyhat)
Sponsored by: Google Summer of Code 2007
Reviewed by (earlier version): Jaakko Heinonen <jh[AT]saunalahti.fi>
Tested by (earlier version): Steve Kargl <sgk[AT]troutmask.apl.washington.edu>
Tested by (earlier version): Martin Voros <martin_voros[AT]yahoo.com>
Tested by (earlier version): swell.k[AT]gmail.com
Tested by (earlier version): joel
Tested by (earlier version): Alexey Shuvaev <shuvaev[AT]physik.uni-wuerzburg.de>
Tested by (earlier version): Arjan van Leeuwen <avleeuwen[AT]gmail.com>

Thanks to gabor@ for building ports for it.
Thanks to erwin@ and kris@ for scheduling the ports build test on pointyhat.
And thanks to many others for their feedback.