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.
Reference Design NetBSD source code, obtained from the pages under
http://www.research.digital.com/SRC/iag . Some of this code (badly)
needs to be cleaned up, and as-is it doesn't compile. However, getting
it in the tree is a start.