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/

spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD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

libc: fix cases of undefined behavior.

These were found by the Undefined Behavious GsoC project at NetBSD:

Avoid undefined behavior in ftok(3)

Do not change the signedness bit with a left shift operation.
Cast to unsigned integer to prevent this.

ftok.c:56:10, left shift of 123456789 by 24 places cannot be represented
in type 'int'
ftok.c:56:10, left shift of 4160 by 24 places cannot be represented in
type 'int'

Avoid undefined behavior in an inet_addr.c

Do not change the signedness bit with a left shift operation.
Cast to unsigned integer to prevent this.

inet_addr.c:218:20, left shift of 131 by 24 places cannot be represented
in type 'int'

Detected with micro-UBSan in the user mode.

Obtained from: NetBSD
MFC after: 2 weeks

libc: 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.

Use ANSI C prototypes. Eliminates -Wold-style-definition warnings.

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.

Change the signature of ftok from (const char *, char) to (const char *, int)

Obtained from: NetBSD (christos)

Fix SCM ID's.

$Id$ -> $FreeBSD$

This is a null commit to log the fact that I have done a repository
copy to bring these files into libc from libcompat. I will enable
them and kill off the libcompat versions on the main branch soon.

PR: step one toward closing misc/6763

Revert $FreeBSD$ to $Id$

Make the long-awaited change from $Id$ to $FreeBSD$

This will make a number of things easier in the future, as well as (finally!)
avoiding the Id-smashing problem which has plagued developers for so long.

Boy, I'm glad we're not using sup anymore. This update would have been
insane otherwise.

Added function and man page for ftok(3), used in conjunction with
the so-called "System V IPC".

Submitted by: jbeukema@HK.Super.Net (John Beukema)
Obtained from: Th. Lockert <tholo@sigmasoft.com>, via NetBSD