Dear all,

I've dusted off and cleaned up a previous attempt to fix the handling
of allocatable or pointer actual arguments to OPTIONAL+VALUE dummies.
The standard says that a non-allocated / non-associated actual argument
in that case shall be treated as non-present.

However, gfortran's calling conventions demand that the presence status
for OPTIONAL+VALUE is passed as a hidden argument, while we need to
pass something on the stack which has the right type.  The solution
is to conditionally create a temporary when needed.

Testcase checked with NAG.

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

Thanks,
Harald