Port contrib/netbsd-tests/kernel/kqueue/... as tests/sys/kqueue/...

proc2_test must be skipped because the invariant tested
(ke.fflags & NOTE_TRACKERR) doesn't pass.

MFC after: 58 days
Submitted by: kib (earlier form)
Sponsored by: EMC / Isilon Storage Division
Differential Revision: https://reviews.freebsd.org/D6172