MFC r273929:

r273929 (by jmmv):

MFV: Import atf-0.21.

Import atf-0.20.

This is a MFC of r261897 and r262000 and should allow all of the atf
tests to pass.

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.

MFC r260491: Use .cpp as the extension for temporary C++ files.

Update atf to 0.18 and remove the code of the deprecated tools.

This is a MFC into stable/10 of:
- r258286 Update notes for imports of atf.
- r258289 MFV: Import atf-0.18.
- r258290 Drop all ATF tools code.

This is "make tinderbox" clean as run on ref10-amd64 with the default
WITHOUT_TESTS option. A "make buildworld" with WITH_TESTS set now works
as well.

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

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

Modify atf::fs::path::get_process_helpers_path API to properly
handle pathing with detail/ tests. Based on patch pushed upstream to
ATF project.

Obtained from: Garrett Cooper <yaneurabeya@gmail.com>

Merge ATF 0.16 from vendor/atf/dist.

Provenance: http://code.google.com/p/kyua
Discussed with: gibbs, gnn, keramida, mdf, mlaier,
Discussed with: Garrett Cooper

Bootstrap dist directory from the initial import of ATF 0.16.

Import ATF version 0,16

Discussed with: gibbs, gnn, keramida, mdf, mlaier,
Discussed with: Garrett Cooper