MFC: r285552
Use strtonum(3) instead of atoi(3)

MFC: r286289
Introduce -P0, creating as many concurrent processes as possible

Relnotes: yes

MFC: r286461
Fix regression in xargs -Px, add more regression tests

MFC: r287004
MFC: r287005
Fix the racy xargs -P0 -n2 test added in r286289

PR: 199976
Submitted by: Nikolai Lifanov <lifanov@mail.lifanov.com>

MFC various moves of tools/regressions/ tests to the new infrastructure.

- r263220 Migrate tools/regression/sbin/ to the new tests layout.
- r263222 Add Makefile missed in r263220.
- r263226 Migrate tools/regression/{usr.bin/lastcomm,usr.sbin}/ to the new tests layout.
- r263227 Migrate most of tools/regression/usr.bin/ to the new tests layout.
- r263345 Expand tabs that sneaked in into spaces.
- r263346 Migrate tools/regression/usr.bin/make/ to the new tests layout.
- r263348 Add Makefiles missed in r263346.
- r263351 Migrate tools/regression/usr.bin/pkill/ to the new tests layout.
- r263388 Mark multi_test as requiring /usr/share/dict/words.
- r263814 Fix path to the run.pl script to let these tests run.
- r264742 Prevent building tests when bootstrapping make.

This is 'make tinderbox' clean.

Migrate most of tools/regression/usr.bin/ to the new tests layout.

I'm starting with the easy cases. The leftovers need to be looked at a
bit more closely.

Note that this change _does_ modify the code of the old tests. This is
required in order to allow the code to locate the data files in the
source directory instead of the current directory, because Kyua
automatically changes the latter to a temporary directory.

Also note that at least one test is known to be broken here. Actually,
the test is not really broken: it's marked as a TODO but unfortunately
Kyua's TAP parser currently does not understand that. Will have to be
fixed separately.

Add a few xargs tests related to -0, -n and quoting.

Switch over to a different, more flexible test output protocol that's
understood by Perl's Test::Harness module and prove(1) commands.

Update README to describe the new protocol. The work's broken down into
two main sets of changes.

First, update the existing test programs (shell scripts and C programs)
to produce output in the ok/not ok format, and to, where possible, also
produce a header describing the number of tests that are expected to be
run.

Second, provide the .t files that actually run the tests. In some cases
these are copies of, or very similar too, scripts that already existed.
I've kept the old scripts around so that it's possible to verify that
behaviour under this new system (in terms of whether or not a test fails)
is identical to the behaviour under the old system.

Add a TODO file.

Convert straightforward regression tests to use regress.m4.

Goodbye, duplicated code, you will certainly not be missed.

Add a test for the -R option.

Prefix tests with PASS and FAIL, to make grepping easier, and note this in
the README.

This affects only the base-system regression tests, of course.

Only exit at the end of a test, exit with the last value of $? that was not 0.

This way the entire regression test is looked at as a pass/fail, not just one
sub-test.

Add regression tests for parts of xargs(1).