Fix simulator return values for _CALL cases. Breakpoint support
and better simulator command/display support. At the sim prompt
you can now:
  Step over or continue past the breakpoint (si or c commands),
  Step multiple statements, (si number)
  Display integer registers separate from floating point:
       p all    (Display integer registers, also pc, lr, etc.)
       p allf   (Floating point registers)
       p alld   (Integer registers print decimal values)
       p rN     (Display register N