Devices related notifications from kernel to userspace

[Matthew Dillon]

    We have a registration infrastructure via make_dev(), but it isn't tied
    into anything.  A devfs backend could use it to construct most of the
    device space.  I'm not sure how pertainant it is but I figured I'd throw
    it in to the pile.

    We definitely don't want to import FreeBSD's myrid locking mechanisms,
    but they shouldn't be too hard to port to ours.  The easiest solution
    is probably to just use lockmgr locks which are fairly well streamlined
    in DragonFly despite being heavy weight.

					-Matt
					Matthew Dillon 
					<dillon at backplane.com>