[Patch, Fortran] PR 85599: warn about short-circuiting of logical expressions for non-pure functions

[Thomas Koenig]

Hi Janus,

> I tested it on a fairly large code base and found no further false
> positives. Also it still regtests cleanly. Ok for trunk?

while I still disagree with this on principle, I will not stand
in the way.

However, one point: I think that the warning should be under a separate
warning, which should then be enabled by -Wextra.
-Waggressive-function-elimination, could be reused for this,
or something else

Regards

	Thomas