include: Remove ancient SCCS tags.

Remove ancient SCCS tags from the tree, automated scripting, with two
minor fixup to keep things compiling. All the common forms in the tree
were removed with a perl script.

Sponsored by: Netflix

Remove $FreeBSD$: one-line .h pattern

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

Add tcgetwinsize(3) and tcsetwinsize(3) to termios

These functions get/set tty winsize respectively, and are trivial wrappers
around corresponding termio ioctls.

The functions are expected to be a part of POSIX.1 issue 8:
https://www.austingroupbugs.net/view.php?id=1151#c3856.
They are currently available in NetBSD and in musl libc.

PR: 251868
Submitted by: Soumendra Ganguly <soumendraganguly@gmail.com>
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D27650

include: further adoption of SPDX licensing ID tags.

Mainly focus on files that use BSD 3-Clause license.

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.

Special thanks to Wind River for providing access to "The Duke of
Highlander" tool: an older (2014) run over FreeBSD tree was useful as a
starting point.

Use __BSD_VISIBLE test instead checking for absense of _POSIX_SOURCE.

The Termios headers <termios.h> and <sys/_termios.h> used sometimes
_POSIX_SOURCE directly to determine if a thing should be exposed to
the user. This circumvented the feature mechanisms of <sys/cdefs.h>.

Submitted by: Sebastian Huber <sebastian.huber@embedded-brains.de>
MFC after: 2 weeks

include: Remove checks for __BSD_VISIBLE where redundant with __XSI_VISIBLE
or __POSIX_VISIBLE.

Whenever <sys/cdefs.h> sets __BSD_VISIBLE to non-zero, it also sets
__POSIX_VISIBLE and __XSI_VISIBLE to the newest version supported.

No functional change is intended.

Add a new libc function: cfmakesane(3).

I've noticed various terminal emulators that need to obtain a sane
default termios structure use very complex `hacks'. Even though POSIX
doesn't provide any functionality for this, extend our termios API with
cfmakesane(3), which is similar to the commonly supported cfmakeraw(3),
except that it fills the termios structure with sane defaults.

Change all code in our base system to use this function, instead of
depending on <sys/ttydefaults.h> to provide TTYDEF_*.

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.

Remove the Berkeley clause 3's.
Add a few $FreeBSD$

Decompose <sys/termios.h>.

The <sys/termios.h> header file is hardlinked to <termios.h>. It
contains both the structures and the flag definitions, but also the C
library interface that's implemented by the C library.

This header file has the typical problem of including too many random
things and being badly ordered. Instead of trying to fix this, decompose
it into two header files:

- <sys/_termios.h>, which contains struct termios and the flags.
- <termios.h>, which includes <sys/_termios.h> and contains the C
library interface.

This means userspace has to include <termios.h> for struct termios,
while kernelspace code has to include <sys/tty.h>. Also add a
<sys/termios.h>, which prints a warning message before including
<termios.h>. I am aware that there are some applications that use this
header file as well.