[patch] Fix internal error on breaking at a multi-locations caller

[Joel Brobecker]

> Based on the documentation of `break', and also my mental model of
> debugging with gdb, I think that the best behavior here would be to
> simply set a single breakpoint here -- the one corresponding to the
> instance that is currently being executed.  Then we don't have to
> worry about the other instances, and we won't set odd breakpoints
> elsewhere.
> 
> What do you (or anybody) think of that?

That's a good point. I actually had a different interpretation
of the "break" command without arguments, but the documentation
is very specific about it. I agree with you.

-- 
Joel