[m-dev.] for review: new debugger command set (part 1 of 4)

[Zoltan Somogyi]

> But there's one thing I want to check.
> In mercury_layout_util.c you replaced `based_framevar' with
> `MR_based_framevar',
> even though `based_framevar(n)' was defined as `MR_based_framevar(n+1)':
> 
> Is that a bug, or is that just an interaction with the other changes?

It is an interaction with other changes.

Zoltan.