sys: Remove $FreeBSD$: one-line .c comment pattern

Remove /^/[*/]\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spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD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

libalias: Style cleanup

libalias is a convolut of various coding styles modified by a series
of different editors enforcing interesting convetions on spacing and
comments.

This patch is a baseline to start with a perfomance rework of
libalias. Upcoming patches should be focus on the code, not on the
style. That's why most annoying style errors should be fixed
beforehand.

Reviewed by: hselasky
Discussed by: emaste
MFC after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D30259

net: clean up empty lines in .c and .h files

sys: 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.

Remove unused inclusion of curses.h

Fix indentation.

Standardise all Swinburne related copyright/licence statements throughout the
tree in preparation for another large code import. Swinburne University is the
legal entity that owns copyright and the 2-clause BSD licence is acceptable.

The university does not require that its CRICOS number be included in source
code. Remove all references from the tree.

MFC after: 3 days

A new jail(8) with a configuration file, to replace the work currently done
by /etc/rc.d/jail.

machine/cpu.h isn't appropriate for this file,so remove it

Add SCTP NAT support.

Submitted by: CAIA (http://caia.swin.edu.au)