[m-rev.] for review: bugfix for io.set_environment_var/4

[Zoltan Somogyi]

On Mon, 18 Apr 2016 09:49:23 +1000 (AEST), Julien Fischer <jfischer at opturion.com> wrote:
> W.r.t to Mark's change: I think we also need to add
> 
>      :- pred have_set_environment_var is semidet.
> 
> so that programs can test whether the unerlying platfrom supports
> modifying the environment.

I think that is a good idea, but you need a better name; that one
suggest you are asking whether you *have* set a *particular* env var,
not whether you *can* set *any* env var.

Zoltan.