- Add "SHOW STACK" support to CPU
- An off-by-one error in checking SDT length was fixed.
- not-present co-processor R/W should not set Bus timeout bit
The 3B2 emulator did not have support for traps, rendering debugging
under the simulator fairly useless. This change adds support for
trap handling. The 'sdb' UNIX debugger under SVR3 should now work
correctly.
