sys: Automated cleanup of cdefs and other formatting

Apply the following automated changes to try to eliminate
no-longer-needed sys/cdefs.h includes as well as now-empty
blank lines in a row.

Remove /^#if.*\n#endif.*\n#include\s+<sys/cdefs.h>.*\n/
Remove /\n+#include\s+<sys/cdefs.h>.*\n+#if.*\n#endif.*\n+/
Remove /\n+#if.*\n#endif.*\n+/
Remove /^#if.*\n#endif.*\n/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/types.h>/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/param.h>/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/capsicum.h>/

Sponsored by: Netflix

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spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD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

libkern: clean up empty lines in .c and .h files

sys/kern: adoption of SPDX licensing ID tags.

Mainly focus on files that use BSD 2-Clause license, however the tool I
was using misidentified 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.

sys: Replace zero with NULL for pointers.

Found with: devel/coccinelle
MFC after: 3 weeks
Differential Revision: https://reviews.freebsd.org/D9694

libkern: Remove obsolete 'register' keyword

Sponsored by: Dell EMC Isilon

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

Split tolower/toupper code from usual xlat16 kiconv table, and make it
possible to do tolower/toupper independently without code conversion.

Submitted by: imura (but bugs are mine)
Obtained from: http://people.freebsd.org/~imura/kiconv/
(1_kiconv_wctype_kern.diff, 1_kiconv_wctype_user.diff)

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

Fix kiconv on the 64bit plathomes.

- Correct idxp pointer to point the properly address of the
each array of the kiconv character conversion tables,
so that character conversion work properly when file
systems are mounted with kiconv options.

- The definition of ICONV_CSMAXDATALEN was also bogus
because it was defined as if all machines were 32bit
computers.

Tested on: amd64
MFC after: 1 month

Make msdosfs long filenames matching case insensitive again.

PR: 59765
Submitted by: Ryuichiro Imura <imura@ryu16.org>

- Support for multibyte charsets in LIBICONV.
- CD9660_ICONV, NTFS_ICONV and MSDOSFS_ICONV kernel options
(with corresponding modules).
- kiconv(3) for loadable charset conversion tables support.

Submitted by: Ryuichiro Imura <imura@ryu16.org>