Remove $FreeBSD$: two-line .h pattern

Remove /^\s*\*\n \*\s+\$FreeBSD\$$\n/

spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD

The SPDX folks have obsoleted the BSD-2-Clause-FreeBSD identifier. Catch
up to that fact and revert to their recommended match of BSD-2-Clause.

Discussed with: pfg
MFC After: 3 days
Sponsored by: Netflix

lib: further adoption of SPDX licensing ID tags.

Mainly focus on files that use BSD 2-Clause license, however the tool I
was using mis-identified 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.

Add support for capturing 'struct ptrace_lwpinfo' for signals
resulting in a process dumping core in the corefile.

Also extend procstat to view select members of 'struct ptrace_lwpinfo'
from the contents of the note.

Sponsored by: Dell EMC Isilon

Add procstat_getauxv function to retrieve a process auxiliary vector.

MFC after: 1 month

Extend libprocstat with functions to retrieve process command line
arguments and environment variables.

Suggested by: stas
Reviewed by: jhb and stas (initial version)
MFC after: 1 month

Add procstat_getosrel function to retrieve a process osrel info.

MFC after: 1 month

Add procstat_getrlimit function to retrieve a process resource limits info.

MFC after: 1 month

Add procstat_getumask function to retrieve a process umask.

MFC after: 1 month

Add procstat_getgroups function to retrieve process groups.

MFC after: 1 month

Make libprocstat(3) extract procstat notes from a process core file.

PR: kern/173723
Suggested by: jhb
Glanced by: kib
MFC after: 1 month