Removed any remnants of soft interrupt dispatching.
Cleaned up a number of comments.
Removed a number of blank lines.
Nuked register keywords.
Made sure code is in sync with interrupt handling for other ARM hardware.
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.
