Remove $FreeBSD$: two-line .h pattern

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

Get rid of the requirement to include SysV IPC headers with _KERNEL
defined in ipcrm by introducing _WANT_SYSVxxx_INTERNALS defines.

Reviewed by: jhb
Sponsored by: DARPA, AFRL
Differential Revision: https://reviews.freebsd.org/D14271

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.

ipcs: fix builds that use gcc
gcc gets annoyed by duplicate declarations

Reported by: sbruno
Reviewed by: sbruno

ipcs: fix warnings (WARNS=1 -> WARNS=6)
- fix shadow warnings
- change type from off_t to size_t which is more correct and avoids
signed/unsigned compare
- use new initializer format to avoid "missing values" warning

Reviewed by: jhb

Spelling fixes for usr.bin/

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

Create the altix project branch. The altix project will add support
for the SGI Altix 350 to FreeBSD/ia64. The hardware used for porting
is a two-module system, consisting of a base compute module and a
CPU expansion module. SGI's NUMAFlex architecture can be an excellent
platform to test CPU affinity and NUMA-aware features in FreeBSD.

- Import the HEAD csup code which is the basis for the cvsmode work.

Add the ability to clean up all shared memory segments which are
unused in one go.

From the original PR:

I've observed that linux apps running under the linuxulator
have a habit of leaving behind shared memory segments which
are unused, but which eventually cause the system to run
out of free segments and these apps will stop working.
ipcrm(1) currently only allows removal of unused message
queues, shared memory segments and semaphores on an individual
basis, or those having a matching (non-zero) key. However
it would often be convenient to just do a complete cleanup
of everything, usually as root.

PR: bin/118292
Submitted by: Callum Gibson <callumgibson@optusnet.com.au>
Not reviewed by: grog@
Approved by: grog@