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

Introduce libxo to procstat(1)

Reviewed by: rodrigc, bapt
Approved by: marcel (mentor)
Relnotes: yes
Sponsored by: ScaleEngine Inc.
Differential Revision: https://reviews.freebsd.org/D2446

Use libprocstat(3) to retrieve process command line arguments and
environment variables.

MFC after: 1 month

Add new options, -e and -x, to display process environment variables
and ELF auxiliary vectors.

MFC after: 2 weeks

- Commit work from libprocstat project. These patches add support for runtime
file and processes information retrieval from the running kernel via sysctl
in the form of new library, libprocstat. The library also supports KVM backend
for analyzing memory crash dumps. Both procstat(1) and fstat(1) utilities have
been modified to take advantage of the library (as the bonus point the fstat(1)
utility no longer need superuser privileges to operate), and the procstat(1)
utility is now able to display information from memory dumps as well.

The newly introduced fuser(1) utility also uses this library and able to operate
via sysctl and kvm backends.

The library is by no means complete (e.g. KVM backend is missing vnode name
resolution routines, and there're no manpages for the library itself) so I
plan to improve it further. I'm commiting it so it will get wider exposure
and review.

We won't be able to MFC this work as it relies on changes in HEAD, which
was introduced some time ago, that break kernel ABI. OTOH we may be able
to merge the library with KVM backend if we really need it there.

Discussed with: rwatson

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

Include param.h instead of types.h before user.h so that the nested
include of param.h can be removed from audit.h.

MFC after: 3 weeks

Add 'COMM' column to a few more output modes of procstat(1). The only
one it's missing from is the VM display, where there's really not room,
and the file output display is looking quite cramped.

Add procstat(1), a process inspection utility. This provides both some
of the missing functionality from procfs(4) and new functionality for
monitoring and debugging specific processes. procstat(1) operates in
the following modes:

-b Display binary information for the process.
-c Display command line arguments for the process.
-f Display file descriptor information for the process.
-k Display the stacks of kernel threads in the process.
-s Display security credential information for the process.
-t Display thread information for the process.
-v Display virtual memory mappings for the process.

Further revision and modes are expected.

Testing, ideas, etc: cognet, sam, Skip Ford <skip at menantico dot com>
Wesley Shields <wxs at atarininja dot org>