swab.c(libc): use a simplified version of byte swapping

This version of swab function simplifies the logic of swapping adjacent
bytes. Previous version of swab() used an arbitrary unrolling, which was
relevant back in the day but unnecessary for modern compilers, as if the
input size is known at compile time, they can do it automatically.

This version of swab() is inspired by musl.
A similar version can be found at: https://github.com/openbsd/src/blob/master/lib/libc/string/swab.c

Signed-off-by: rilysh <nightquick@proton.me>
Reviewed by: imp
Pull Request: https://github.com/freebsd/freebsd-src/pull/1086

lib: 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

libc: Purge unneeded cdefs.h

These sys/cdefs.h are not needed. Purge them. They are mostly left-over
from the $FreeBSD$ removal. A few in libc are still required for macros
that cdefs.h defines. Keep those.

Sponsored by: Netflix
Differential Revision: https://reviews.freebsd.org/D42385

Remove $FreeBSD$: one-line .c pattern

Remove /^[\s*]*__FBSDID\("\$FreeBSD\$"\);?\s*\n/

Fix truncation when ssize_t is larger than MAX_INT

Casting to int truncates size on some platforms, resulting swab not
copying all the data. Cast len to size_t to avoid right shifting a
signed value: we know here it's > 0, so we can safely cast it w/o losing
precision.

In addition, be more careful with signedness of char pointers and
temporaries. Downgrade tmp from unsigned long to unsigned char since
we're only reading and writing characters.

Reviewed by: imp
Pull Request: https://github.com/freebsd/freebsd-src/pull/516

General 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.

Renumber clauses to reduce diffs to other versions

NetBSD, OpenBSD, and Android's Bionic number the clauses 1 through 3,
so follow suit to make comparison easier.

POSIX mandates that swab do nothing when len < 0

PR: kern/140690
Submitted by: Jeremy Huddleston <jeremyhu@apple.com>
Approved by: cperciva
MFC after: 2 weeks

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.

Per Regents of the University of Calfornia letter, remove advertising
clause.

# If I've done so improperly on a file, please let me know.

According to the information on:
http://www.opengroup.org/onlinepubs/009695399/functions/swab.html
the prototype for swab() should be in <unistd.h> and not in <string.h>.
Move it, and update to match SUS. Leave the prototype in string.h for
now, for backwards compat.

PR: 74751
Submitted by: Craig Rodrigues <rodrigc@crodrigues.org>
Discussed with: das

- Convert the function definition to declare its arguments
in the ANSI-C format.
- Change the code a bit to hopefully save some cycles.
I.e. (simplified) change

a = b + 1;
while (--b & 0x7)
/* ... */
to
a = b;
for (; b & 0x7; b--)
/* ... */
and
while (--a >= 0)
/* ... */
to
for (; a > 0; a--)
/* ... */
- Equip two function arguments of swab() with the 'restrict'
type qualifier in form of the '__restrict' macro. This is
specified by POSIX.1-2001.

Remove 'register' keyword.

rcsid[]->__FBSDID

Make the rcsid and FreeBSD IDs more sane in the wcs* and wmem* files.
Do the same for the non-wcs*/wmem* files while I'm here.

BSD 4.4 Lite Lib Sources