Add support for trap recovery:

Add support for trap recovery:
- New condition types for hardware traps have been added.
- The stack parser knows how to parse (heuristically) the trap
recovery information.
- The debugger prints a description of the context of the trap.
- hardware-trap-frame/print-registers and
hardware-trap-frame/print-stack can be used on stack-frames of type
hardware-trap to display more information.
- The debugger's Y command (new) prints the stack frame structure
corresponding to the current subproblem.