Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

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

MFC various fixes to the tools/regression/ tests.

- r262953 Fix m4 tests so that they run cleanly with prove.
- r262954 Fix printf tests so that they run cleanly with prove.
- r262959 Fix sed tests so that they run cleanly with prove.
- r262960 Fix yacc tests so that they run cleanly with prove.
- r262961 Fix pkill tests so that they run cleanly with prove.
- r262962 Fix ncal tests so that they run cleanly with prove.
- r263081 Fix lastcomm tests under amd64.
- r263082 Only run the make tests when make is fmake.
- r263083 Fix sa tests.
- r263084 Turn a test precondition into a skip in the mdconfig tests.
- r263085 Make the strerror tests work without libtap.
- r263087 Remove broken tests for eui64_line.
- r263221 Change etcupdate tests to return 1 on test failures.
- r263352 Make the priv test program exit with non-zero if any failures are detected.
- r263353 errx prepends the program name to the message; don't do it by hand.
- r263362 Include strings.h so that bpf_filter.c can be built in userland.

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

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

Allow strerror(0) and strerror_r(0, ...).

Of course, strerror_r() may still fail with ERANGE.

Although the POSIX specification said this could fail with EINVAL and
doing this likely indicates invalid use of errno, most other
implementations permitted it, various POSIX testsuites require it to
work (matching the older sys_errlist array) and apparently some
applications depend on it.

PR: standards/151316
MFC after: 1 week

Tests for wcscasecmp(), wcsnlen(), and stpncpy().

Add to CFLAGS, rather than overriding it. Use LDFLAGS for the -L option,
and LDLIBS to specify -ltap.

Submitted by: ru

Link against libtap (ports/devel/libtap). Replace the calls to assert()
with calls to libtap::ok1(), and make sure the correct number of tests is
planned for, and that the exit code is correct.

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.

Add regression test for strerror()/strerror_r().

Based on: src/lib/libc/string/strerror.c (rev 1.8)