[patch, fortran] Fix a few false positive warnings with unused/undefined warnings

[Thomas Koenig]

Hi Jerry,

>> what it says in the ChangeLog.  Regression-tested. OK for trunk?
> 
> 
> Looks OK Thomas. Thanks for the patch.

Committed as https://gcc.gnu.org/g:ea991f752fc2a65a887c64190d8cad415edac8c9.

Thanks a lot for the review!

Best regards

	Thomas