[ddbg] ps should print source of current frame

[Jascha Wetzel]

Bill Baxter wrote:
> Thanks for adding the 'ps' previously.  Makes debugging from the command 
> line much much easier.
 >
> But I just noticed that it doesn't honor the current frame setting.  I 
> think ps should print the source of the current location in the current 
> frame, not the current location in the topmost frame.
> 
> This is how gdb and other debuggers I've used do it, and it makes sense 
> I think.
> 
> --bb

you're right. i don't know why i missed that, since "da" already uses 
the frame start/end for disassembly. i'll fix it for the next release.