[m-rev.] for review: fix mantis bug 544

[Julien Fischer]

On Mon, 7 Feb 2022, Julien Fischer wrote:

> Once this is committed, I'll set up a machine to bootcheck the trunk
> in a bunch of hlc grades; provided that all passes I will merge it on to
> the release branch -- the map fix will go on to the release branch
> regardless.

Those bootchecks have passed at all optimisation levels, with and
without intermodule-optimisation in all of the grades hlc.gc.tr, hlc.gc
and hlc.par.gc.  The machine is currently half through doing bootchecks
in hlc.gc.memprof, but at this point I think it is fairly safe to merge
this one on to the relaese branch -- I will do so this evening.

Julien.