Dear all,

one cannot pass a NULL actual argument to a procedure without an
explicit interface.  This is detected and reported by NAG and Intel.
(Cray accepts this silently, and some other brands ICE.)

The testcase by Gerhard even tricked gfortran into inconsistent
behavior which could lead to an ICE with -fallow-argument-mismatch,
or silently accepting invalid code.

The solution is to reject such code, see attached patch.

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

As this is marked as a regression which started at v7,
OK for backports to open branches?

Thanks,
Harald