[gfortran] intrinsic GETARG and IARGC

[Paul Brook]

> 2004-06-09  Bud Davis  <bdavis9659@comcast.net>
>
> 	* intrinsics/args.c: Implement GETARG and IARGC.

I've applied this with one minor change.

This implementation breaks when the default integer kind is not 4, but we can 
probably fix that in the frontend.

Paul

> + void
> + prefix(iargc) ()

Should return GFC_INTEGER_4.