Dear all,

here's a first patch addressing issues with NULL as actual argument:
if the dummy is assumed-rank or assumed length, MOLD shall be present.

There is also an interp on interoperability of c_sizeof and NULL
pointers, for which we have a partially incorrect testcase
(gfortran.dg/pr101329.f90) which gets fixed.

See https://j3-fortran.org/doc/year/22/22-101r1.txt for more.

Furthermore, nested NULL()s are now handled.

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

I consider this part as safe and would like to backport to 13-branch.
Objections?

Thanks,
Harald