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 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 r262868

Only use -lpthread for unix_seqpacket_test, not for all test programs.

MFC r262894

kern/Makefile
Set WARNS=5 for all files in this directory
kern/unix_seqpacket_test.c
Fix compiler warnings. Most were benign, but rcvbuf_oversized
wasn't working as intended because I forgot to set the buffer sizes.

MFC r261081, r261133, and r261615

r261081
Replace the old unix_seqpacket and unix_seqpacket_exercise
tests, which were a little broken and not automatable, with
unix_seqpacket_test. It's coverage is a superset of the old
tests and it uses ATF. It includes test cases for bugs
kern/185813 and kern/185812.

r261133
Fix the Makefiles so that the tests I submitted in r261081 will
actually get built.

r261615
tests/sys/Makefile
use TESTS_SUBDIRS for kern instead of SUBDIRS. I don't
think it makes a difference in this case, but
TESTS_SUBDIRS is generally correct for subdirectories
that contain tests.

Replace the old unix_seqpacket and unix_seqpacket_exercise tests, which
were a little broken and not automatable, with unix_seqpacket_test.
It's coverage is a superset of the old tests and it uses ATF. It
includes test cases for bugs kern/185813 and kern/185812.

PR: kern/185812
PR: kern/185813
Sponsored by: Spectra Logic
MFC after: 2 weeks