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spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD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

sort: remove NLS support

NLS support for sort(1) is:
1/ incomplete: many error string are not using nls
2/ only covers hu_HU.ISO8859-2

sort: Fix message catalogue usage

- Check that catopen() succeeded before calling catclose(). musl will
crash in the latter if the catalogue descriptor is -1.
- Keep the message catalogue open for most of sort(1)'s actual
operation.
- Don't use catgets(3) to print error messages if catopen(3) had failed.

Reviewed by: arichardson, emaste
MFC after: 1 week
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D34081

sort: Cache value of MB_CUR_MAX

Every usage of MB_CUR_MAX results in a call to __mb_cur_max. This is
inefficient and redundant. Caching the value of MB_CUR_MAX in a global
variable removes these calls and speeds up the runtime of sort. For
numeric sorting, runtime is almost halved in some tests.

PR: 255551
PR: 255840
Reviewed by: markj
MFC after: 1 week
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D30170

various: general 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.

No functional change intended.

Various style(9) fixes and typos in grep, sort and patch.

MFC after: 3 days

- Update Oleg Moskalenko's email address

Requested by: Oleg Moskalenko <mom040267@gmail.com>

- Use unsigned int for values obtained with sysctlbyname(). This fixes
sparc64 performance problems.

Submitted by: Oleg Moskalenko <oleg.moskalenko@citrix.com>
Tested by: trasz

- Portability changes for ARM
- Allow larger sort memory on 64-bit platforms

Submitted by: Oleg Moskalenko <oleg.moskalenko@citrix.com>

- Remove the UNUSED_ARG macro and use __unused in argument lists

Reviewed by: dim
MFC after: 3 days

In usr.bin/sort, use another method of silencing warnings about unused
arguments, which does not trigger self-assignment warnings in certain
circumstances (for example, using clang with ccache).

MFC after: 3 days

- Only use multi-threading for large files
- Do not use mmap() by default; it can be enabled by --mmap
- Add some minor optimizations for -u
- Update manual page according to the changes

Submitted by: Oleg Moskalenko <oleg.moskalenko@citrix.com>

Add a BSD-licensed sort rewrite that was started by me and later completed
with the major functionality and optimizations by Oleg Moskalenko.
It is compatible with the latest version of POSIX and the current GNU sort
version that we have in base. Beside this, it implements all the
functionality introduced in later versions of GNU sort. For now, it will
be installed as "bsdsort", keeping GNU sort as the default sort
implementation.

Remove old sort files to _actually_ build it from contrib sources

Forgotten by: des

Remove __P

Vendor import NETBSD's sort(1). This will be a replacement for
our GNU sort, as discussed 6 months or more ago.