1. Create and use an interrupt stack.
2. Longword align kernel stack.
3. Copy/clear primitives could be tuned.
4. Sendsig/sigreturn are way bogus.
5. Ditto for AST and software interrupt emulation.
6. Improved external virtual address cache management;
   current implementation is somewhat arbitrary and conservative.
7. Cut clock rate back to 20ms?
8. Inlining (GCC asm?) of low level stuff. (e.g. spl's)
9. DIO-II support (can't map entire address space like we do DIO-I,
   must create "windows").
10.Nail down kernel u-area address; i.e. insulate it from changes
   in the size of other SYSMAPs.