Dear all,

here's the first part of an attempt to fix issues with optional
dummy arguments as actual arguments to optional dummies.  This patch
rectifies the case of scalar dummies with the VALUE attribute,
which in gfortran's argument passing convention are passed on the
stack when they are of intrinsic type, and have a hidden variable
for the presence status.

The testcase tries to cover valid combinations of actual and dummy
argument.  A few tests that are not standard-conforming but would
still work with gfortran (due to the argument passing convention)
are left there but commented out with a pointer to the standard
(thanks, Mikael!).

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

Thanks,
Harald