[Ada] PATCH: untested CALL_EXPR updates

[Richard Kenner]

> A quick glance at this code didn't tell me how to determine in
> advance how many arguments were being passed and hence how big of an
> array to allocate, but it'll probably be easy for somebody already
> familiar with the Ada-specific data structures.  

No, it's just like what GCC does in places: walk the arglist twice, once
to just count it and once to do the real work.