[m-rev.] for review: warn about unneeded initial and final state vars

[Zoltan Somogyi]

On Fri, 16 May 2025 03:46:37 +1000 (AEST), "Zoltan Somogyi" <zoltan.somogyi at runbox.com> wrote:
> For review by anyone.

In the absence of a review, I have committed the changes
to options.m (with the user-visible change commented out)
and handle_options.m, in order to make it possible to add
the new options to Mercury.options files sooner.

I would still welcome a review.

Zoltan.