sys: 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

sys: Remove $FreeBSD$: one-line .h pattern

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

sys: 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 copyright clause 4

Renumber cluase 4 to 3, per what everybody else did when BSD granted
them permission to remove clause 3. My insistance on keeping the same
numbering for legal reasons is too pedantic, so give up on that point.

Submitted by: Jan Schaumann <jschauma@stevens.edu>
Pull Request: https://github.com/freebsd/freebsd/pull/96

Fix types of some values in machine/_limits.h.

On some architectures UCHAR_MAX and USHRT_MAX had type unsigned int.
However, lacking integer suffixes for types smaller than int, their type
should correspond to that of an object of type unsigned char (or short)
when used in an expression with objects of type int. In that case unsigned
char (short) are promoted to int (i.e. signed) so the type of UCHAR_MAX and
USHRT_MAX should also be int.

Where MIN/MAX constants implicitly have the correct type the suffix has
been removed.

While here, correct some comments.

Reviewed by: bde
Approved by: kib (mentor)

Remove unused support for 64 bit long on 32 bit architectures.

It was used mainly to discover and fix some 64-bit portability problems
before 64-bit arches were widely available.

Discussed with: bde
Approved by: kib (mentor)

A new jail(8) with a configuration file, to replace the work currently done
by /etc/rc.d/jail.

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

Move MINSIGSTKSZ from <machine/signal.h> to <machine/_limits.h> and rename
it to __MINSIGSTKSZ. Define MINSIGSTKSZ in <sys/signal.h>.

This is done in order to use MINSIGSTKSZ for the macro PTHREAD_STACK_MIN
in <pthread.h> (soon <limits.h>) without having to include the whole
<sys/signal.h> header.

Discussed with: bde

Start all license statements with /*-

Remove advertising clause from University of California Regent's license,
per letter dated July 22, 1999.

Approved by: core

sys/sys/limits.h:

- Fix visibilty test for LONG_BIT and WORD_BIT. `#if defined(__FOO_VISIBLE)'
is alays wrong because __FOO_VISIBLE is always defined (to 0 for
invisibility).

sys/<arch>/include/limits.h
sys/<arch>/include/_limits.h:

- Style fixes.

Submitted by: bde
Reviewed by: bsdmike
Approved by: re (scottl)

Style fixes.
Remove DBL_DIG, DBL_MIN, DBL_MAX and their FLT_ counterparts, they
were marked for deprecation ever since SUSv1 at least.
Only define ULLONG_MIN/MAX and LLONG_MAX if long long type is
supported.
Restore a lost comment in MI _limits.h file and remove it from
sys/limits.h where it does not belong.

Add a new sys/limits.h file which in turn depends on machine/_limits.h
to get actual constant values. This is in preparation for machine/limits.h
retirement.

Discussed on: standards@
Submitted by: Craig Rodrigues <rodrigc@attbi.com> (*)
Modified by: kan

MB_LEN_MAX is not MD, move it to the MI limits.h.

Create a new header <machine/_stdint.h> for storing MD parts of
<stdint.h>. Previously, parts were defined in <machine/ansi.h> and
<machine/limits.h>. This resulted in two problems:
(1) Defining macros in <machine/ansi.h> gets in the way of that
header only defining types.
(2) Defining C99 limits in <machine/limits.h> adds pollution to
<limits.h>.

machine/limits.h
(taken from i386/include/limits.h rev 1.19)