[RFC] Support of IEEE modules, first draft for comments

[FX]

> AFAICT "dg-add-options ieee" is handled by add_options_for_ieee in
> gcc/testsuite/lib/target-supports.exp. I don't think add-ieee-options
> in gcc/testsuite/lib/fortran-torture.exp is called by anything (but
> I may have overlooked something).

Thanks Dominique (and Arjen who helped off-list). You’re right, add_options_for_ieee is the right codepath for stuff in the gfortran.dg/ directory. add-ieee-options in fortran-torture.exp is called by gfortran.fortran-torture/execute/intrinsic_nearest.x and others in that directory.

FX