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/

Vendor import of stripped libc++ trunk r366426 (just before the release_90 branch
point):

https://llvm.org/svn/llvm-project/libcxx/trunk@366426

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.

Vendor import of libc++ trunk r256633:
https://llvm.org/svn/llvm-project/libcxx/trunk@256633

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 convenience macro for the returns_twice attribute, and apply it to
the prototypes of the appropriate functions (getcontext, savectx,
setjmp, sigsetjmp and vfork).

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.

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

Namespace: _setjmp() and _longjmp() are XSI extensions.

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

Fix namespace issues by using visibility conditionals from
<sys/cdefs.h>. Sort function prototypes.

Breath deep and take __P out of the system include files.

# This appears to not break X11, but I'm having problems compiling the
# glide part of the server with or without this patch, so I can't tell
# for sure.

Suggested by: bde
Move sigjmp_buf and jmp_buf structure definitions to machine/setjmp.h
so that i386 can continue to use int as the basic register type and
alpha can use long. Bruce was concerned about possible differing
alignment. I've left the definition of _JBLEN in machine/setjmp.h
even though Bruce's example used the number directly. I don't know if
any other code relies on _JBLEN, so I left it to avoid potential
breakage.

Move _JBLEN definition to <machine/setjmp.h> like on NetBSD. Remove
definitions for architectures that we don't have libc MD source for.

Change 'int' to 'long' in sigjmp_buf and jmp_buf structures so
that they are suitable for the register size on both i386 and alpha.
Although FreeBSD defines these structures differently to NetBSD,
the element size is now the same.

If Bruce doesn't like this [8-)], we'll need to add a typedef to
each <machine/setjmp.h> and use that in <setjmp.h>.

Don't use __dead or __pure in user code. They were obfuscations
for gcc >= 2.5 and no-ops for gcc >= 2.6. Converted to use __dead2
or __pure2 where it wasn't already done, except in math.h where use
of __pure was mostly wrong.

Delete `vax' (and `i386' and `hp300' etc.) namespace pollution.
Our one supported compiler always defines the double-underscore variant,
so always use that.

Noticed by Bruce Evans after a report by John Capo.

Improve error detection and handling:
Reduce _JBLEN for the i386 to what is actually used.
Encapsulate jmp_buf and sigjmp_buf in structs.
Enlarge jmp_buf to the same size as sigjmp_buf.
Declare *longjmp as non-returning.

Remove stale comments about sig*jmp not being implemented.

BSD 4.4 Lite Include Sources