[Bug fortran/67982] Incorrect -Wunused-function warning

[dominiq at lps dot ens.fr]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67982

--- Comment #4 from Dominique d'Humieres <dominiq at lps dot ens.fr> ---
> Otherwise this might need bisection.

Note that I cannot do easily the bissection on darwin due to a lot of bootstrap
failures in the range r224161-r224647. If nobody volunteer to do the bisection,
I'll close this PR as FIXED on trunk (6.0).