Lots of changes, including:
- Support for AlphaStation 200, 250, 255, 400
- Untested support for UDB, Multia, AXPpci33 (Noname)
- Support for Personal Workstation 433a/433au, 500a/500au, 600a/600au (Miata)
- Some minor fixes and improvements to interrupt handling.
Submitted by: Andrew Gallatin <gallatin@cs.duke.edu> (AS200, Miata)
Obtained from: NetBSD (some code for AS200, Miata, Noname)