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spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD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: drop "All rights reserved" from Foundation copyrights

This has already been done for most files that have the Foundation as
the only listed copyright holder. Do it now for files that list
multiple copyright holders, but have the Foundation copyright in its own
section.

Sponsored by: The FreeBSD Foundation

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.

Implement xlocale APIs from Darwin, mainly for use by libc++. This adds a
load of _l suffixed versions of various standard library functions that use
the global locale, making them take an explicit locale parameter. Also
adds support for per-thread locales. This work was funded by the FreeBSD
Foundation.

Please test any code you have that uses the C standard locale functions!

Reviewed by: das (gdtoa changes)
Approved by: dim (mentor)

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.

Introduce a local variable and use it instead of passed in parameter
to get rid of restrict qualifier discarding. This lets libc compile
cleanly in gnu99 mode.

Suggested by: kib, christoph.mallon at gmx.de
Approved by: kib (mentor)

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

Implement the GNU extensions of mbsnrtowcs() and wcsnrtombs(). These are
convenient when the source string isn't null-terminated.

Implement the other conversion functions (mbstowcs(), mbsrtowcs(), wcstombs(),
wcsrtombs()) in terms of these new functions.

Allow encoding modules to override the default implementations of
mbsrtowcs() and wcsrtombs(). Provide a fast implementation for the
trivial "NONE" encoding.

Begin in the initial shift state in mbstowcs() and wcstombs().
(This change is non-functional since nothing uses states yet.)

Prepare to handle state-dependent encodings. This mainly involves not
taking shortcuts when it comes to storing and passing around conversion
states.

Implement mbstowcs() as a wrapper around mbsrtowcs(), and wcstombs()
as a wrapper around wcsrtombs().

Style sweep.

Style: One space between "restrict" qualifier and "*".

Add restrict qualifiers to the arguments of mbstowcs, mbtowc() and
wcstombs().

Implement the XSI extension which allows the destination string to be
NULL, and returns the number of bytes that would be required to store
the result of the conversion without storing anything.

PR: 17694

Split ansi.c into a separate source file for each function.