MFC r326276:

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.

MFC r309232-309234:

r309232: Fix an obvious typo.
r309233: Eliminate variables that are computed, assigned but
never used.
r309234: pages and psize are always assigned, so there is no
need to initialize them as zero.

Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Cleanup unnecessary semicolons from utilities we all love.

sort(1): Cleanups and a small memory leak.

Remove useless check for leading blanks in the month name. The
code didn't adjust len after stripping blanks so even if a month
*did* start with a blank we'd end up copying garbage at the end.
Also convert a malloc + memcpy to strdup and fix a memory leak in
the wide char version if mbstowcs() fails.
Originally from Andre Smagin.

Obtained from: OpenBSD (CVS rev. 1.2, 1.3)
MFC after: 1 week

Revert (partial) r281123, r281125:
sort: style knits / cleanups.

Our style guide(9) specifies that in absence of local variables
an empty line must be inserted.

Pointed out by: eadler

sort: style knits / cleanups.

Obtained from: OpenBSD

sort: Fix a comment.

Obtained from: OpenBSD

- Update Oleg Moskalenko's email address

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

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

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

- 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>

- Eliminate initializations if global variables. Compilers are not
required to optimize these so it may result in larger binary size.

Pointed out by: kib

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.