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 r266473,267331,267511:

Use an intermediate target to associate with _SUBDIR which is marked .MAKE
this allows make -n to do tree walks as expected without
doing anything else (as intended).
Use prefix _sub. to help avoid conflict with any real target.

Put the test suite in its own tests.txz distribution file.
Force all the contents of /usr/tests to go into a separate distribution
file so that users of binary releases can easily choose to not install

Create a mechanism for providing fine-grained build order dependencies
during SUBDIR_PARALLEL builds. This augments the coarse .WAIT mechanism,
which is still useful if you've got a situation such as "almost everything
depends on A and B".

MFC refactoring of the *.test.mk files.

- r263161 Make bsd.test.mk the only public mk fragment for the building of tests.
- r263172 Move FreeBSD Test Suite-specific code to a suite.test.mk file.
- r263204 Add some documentation for bsd.test.mk.
- r263217 Document support for TAP-compliant Perl test programs.

This is "make tinderbox" clean.

MFC a couple of improvements to the test suite mk files.

- r260632 Support defining test program metadata from the Makefiles.
- r260633 Support perl-based TAP-compliant test programs.

MFC various fixes for the ATF tests.

- r260505 Allow tests to provide a Kyuafile when they relied on auto-generation.
- r260525 Respect the original layout of the atf-{c,c++} tests.
- r260526 Fix path to the process_helpers for the libatf-c++ tests.
- r260576 Generate and install pkg-config files for atf.
- r260577 Add atf pkg-config files from the vendor branch.
- r260584 Prevent misc_helpers from running as a test.

Split and extend bsd.test.mk into {atf,plain,tap}.test.mk.

This is a MFC of:

- r256761 Clearly split the logic to build ATF and plain tests apart.
- r256762 Add the automatic generation of Atffile files.
- r256763 Add the automatic generation of Kyuafile files.
- r256764 Plug atf-run into the 'test' target.
- r256765 Plug kyua into the 'test' target.
- r257096 Move the TESTSBASE definition to bsd.own.mk.
- r257099 Add missing plain.test.mk.
- r258297 Remove registration of C++ test programs into PROGS.
- r258298 Fix the build of plain test programs.
- r258551 Install plain.test.mk.
- r259208 Add tap.test.mk.

Approved by: rpaulo (mentor)

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

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

Enable ATF testing.

Submitted by: Garrett Cooper
Approved by: marcel (mentor)