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

Use TAP_TESTS_PERL to register the legacy_test in bin/pax.

Redo r260586 by using the new functionality in tap.test.mk to transparently
support perl-based test programs.

As a side-effect, we get rid of an explicit path to /usr/bin/perl by
replacing it with /usr/local/bin/perl (or as defined in tap.test.mk).

This also fixes the name of the legacy_test source file because this should
have always been legacy_test.pl and not legacy_test.sh. My mistake when
originally moving the code around without realizing that this was a perl
script.

MFC after: 5 days

Migrate tools/regression/bin/ tests to the new layout.

This change is a proof of concept on how to easily integrate existing
tests from the tools/regression/ hierarchy into the /usr/tests/ test
suite and on how to adapt them to the new layout for src.

To achieve these goals, this change:

- Moves tests from tools/regression/bin/<tool>/ to bin/<tool>/tests/.
- Renames the previous regress.sh files to legacy_test.sh.
- Adds Makefiles to build and install the tests and all their supporting
data files into /usr/tests/bin/.
- Plugs the legacy_test test programs into the test suite using the new
TAP backend for Kyua (appearing in 0.8) so that the code of the test
programs does not have to change.
- Registers the new directories in the BSD.test.dist mtree file.

Reviewed by: freebsd-testing
Approved by: rpaulo (mentor)

Correct an out-by-one error when earlying out ustar filenames that
are too long. Filenames escaping this test are caught later on,
so the bug doesn't cause any breakage.

Document the correct ustar limitations in pax. As I have no access
to the IEEE 1003.2 spec, I can only assume that the limitations
imposed are in fact correct.

Add regression tests for the filename limitations imposed by pax.

MFC after: 3 weeks