MFC r326276:

various: general adoption of SPDX licensing ID tags.

Mainly focus on files that use BSD 2-Clause license, however the tool I
was using misidentified many licenses so this was mostly a manual - error
prone - task.

The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.

No functional change intended.

Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

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

Style tweak.

Approved by: re (kib)
MFC after: 3 days

If the label being printed by getpmac(8) is empty, then don't print a
carriage return.

Obtained from: TrustedBSD Project
MFC after: 3 days

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)

Userland signed char fixes for PPC build. Problems were using a char
return for getopt() and comparing to -1, ditto with fgetc() and EOF,
and using the kg_nice value from <sys/user.h>

Submitted by: Stefan Farfeleder <stefan@fafoe.narf.at>
Reviewed by: obrien, bde (a while back)
Tested lightly on: ppc, i386, make universe

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