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

WARNS?=6 cleanup for [gs]et[fp]mac:
- Constify structure members that should not be changed
during process.
- Apply static where needed
- signed/unsigned madness
- Bump WARNS?= levels from 2 to 6

(this is a diff reduction for a subsequent commit against these
Makefile's)

Introduce simple command line tools to manage MAC labels on processes and
files. Basically wrappers for mac_{get,set}_{file,link,pid,proc}(3).
Man pages to be updated shortly.

Approved by: re
Obtained from: TrustedBSD Project
Sponsored by: DARPA, Network Associates Laboratories