Only detach the USB device you disconnected, fix a regression reported
by guenther@.

While here set the dying flag of the disconnected device so that most of
the DVACT_ACTIVATE handlers can go.
Remove incorrect comment about how autoconf(9) works and document
that usbd_detach() should only be called by the thread doing USB
bus exploration to prevent attach/detach races.
move macppc abtn(4) driver from workq to taskq

thanks to Fred Crowson (fred () crowsons ! net) who was able
to make sure his cd would still eject when the button was pushed,
and stsp@ who lent me his macppc laptop
essentially mechanical conversion of softraid rebuild from
workq to taskq

ok jsing@
Make disabling last cipher work.
From Thijs Alkemade via OpenSSL trunk
ok miod@
Kill a bunch of DVACT_DEACTIVATE handlers whose only purpose were to
set the 'dying' flag of a device.  Such handlers are useless now that
usbd_detach() already set this flag.

Even if the purpose of this flag is questionnable on OpenBSD because
DVACT_DEACTIVATE acts as a pre-detach event, this is just a first small
step towards the simplification of the autoconf(9) device states.

This cleaning is now possible thanks to the work of pirofti@ to convert
all the USB drivers to properly use usbd_is_dying().

Discussed many times with deraadt@
Move things around (no change):
- some unofficial services became official
- move kerberos next to afs
Use the correct poll interval for HS root hub before it gets copied, no
real impact since this descriptor is not used in the kernel. From NetBSD.