[m-rev.] for post-commit review: improve documentation of query options

[Zoltan Somogyi]

On Sat, 15 Jan 2022 00:38:09 +1100 (AEDT), Julien Fischer <jfischer at opturion.com> wrote:
> >> I just had a grep
> >> through the G12 source code which is using them all over the place.
> >
> > Using them for what purpose, if I may ask?
> 
> Their intended purpose: controlling what set of grades a library is
> installed in.

Sorry for harping on about this, but I still have questions.

- What library is this sentence talking about? Is it the Mercury
  standard library, or some other?

- How does setting setting up the value of an accumulating option
   *control* anything? What code uses the value of the option
  to decide in what grades to install anything? The output of
  "egrep -w libgrades" did not reveal any such code to me.

Zoltan.