Dear all,

the Fortran standard requires an explicit procedure interface in certain
situations, such as when they have a BIND(C) attribute (F2018:15.4.2.2).
The attached patch adds a check for this.

Regtested on x86_64-pc-linux-gnu.  OK for mainline?

The PR marks this as a long-time regression, so it might be backported
to all open branches.

Thanks,
Harald