gfortran: enabling specific warnings for a used but not set variable, and a set but not used variable

[Dominique d'Humières]

This is tracked by bugzilla pr61181 (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61181).

As a general comment post concerning gfortran should go to fortran@gcc.gnu.org.

Cheers,

Dominique