MFC r290913,r291181:

MFC r290913,r291181:

r290913:

Port contrib/netbsd-tests/kernel/t_mqueue.c to FreeBSD

- Add missing headers
- Ensure mqueuefs is loaded
- Make sure the mqueuefs path is absolute and relative to /
- Cast the result of mq_open returning -1 to (mqd_t) to mute a compiler
  warning

Sponsored by: EMC / Isilon Storage Division

r291181:

Integrate contrib/netbsd-tests/kernel/t_mqueue into the FreeBSD test
suite as tests/sys/kern/mqueue_test

git-svn-id: svn://svn.freebsd.org/base/stable/10@291764 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f