This release fixes notification (un)registration and should be
fully-supported on modern FreeBSD (7.2+) releases.
POSIX_MQ#notify=nil correctly unregister notification requests.
POSIX_MQ#notify=false now provids the no-op SIGEV_NONE
functionality. Under FreeBSD, using IO.select on POSIX_MQ
objects is now possible as it has always been under Linux.