[reverse RFA] no singlestep-over-BP in reverse

[Joel Brobecker]

> And I believe that consistent behavior / semantics should be:
> 
>    If you tell me that you are stopped at instruction 1000,
>    regardless of whether you were going forward or backward
>    when you got there, then I will expect that if I tell you
>    to execute forward, you will execute the instruction at
>    1000.

This makes total sense to me. I think I would be very confused
by the debugger if I started going back and forth with a debugger
that didn't follow the semantics above.

-- 
Joel