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