MFC r290914:

Integrate tools/regression/pipe in to the FreeBSD test suite as
tests/sys/kern/pipe

- Fix style(9) bugs
- Fix compiler warnings
- Use `nitems(x)` instead of `sizeof(x) / sizeof(*x)` pattern

The testcases will be converted over to ATF eventually, but for now will be
integrated in as plain C tests

Sponsored by: EMC / Isilon Storage Division

Integrate tools/regression/pipe in to the FreeBSD test suite as
tests/sys/kern/pipe

- Fix style(9) bugs
- Fix compiler warnings
- Use `nitems(x)` instead of `sizeof(x) / sizeof(*x)` pattern

The testcases will be converted over to ATF eventually, but for now will be
integrated in as plain C tests

MFC after: 1 week
Sponsored by: EMC / Isilon Storage Division

NO_MAN= has been deprecated in favor of MAN= for some time, go ahead
and finish the job. ncurses is now the only Makefile in the tree that
uses it since it wasn't a simple mechanical change, and will be
addressed in a future commit.

Start the dreaded NOFOO -> NO_FOO conversion.

OK'ed by: core

For variables that are only checked with defined(), don't provide
any fake value.

Add a regression test for the big pipe bug.

Suggested by: silby