timeout()/untimeout() API:
- Clients supply callout handle storage, thus eliminating problems of
resource allocation.
- Insertion and removal of callouts is constant time, important as
this facility is used quite a lot in the kernel.
The old timeout()/untimeout() API has been removed from the kernel.
- Removed mainbus specific code and moved the basic drivers from
arm32/mainbus to arm32/dev. Added code so that these drivers
will support multiple attachments from different ARM busses.