[PATCH][Ada] fix ada/24855

[Arnaud Charlet]

> From Joel, needed to progress on building cross arm-rtems with Ada
> enabled.
> 
> Ok to commit?

Not without more explanations. Where did you test this change ?
Could you confirm that stdarg.h is guaranteed to be always available ?
Also, the placement of the include seems incorrect to me. Finally,
it would be good to give a small recap of what the problem is, so that
people do not have to go back to the PR to get this info while reviewing
your proposed change.

(Note that I have a change that will be done today which splits
raise.c into raise.c and raise-gcc.c; your patch will apply to
raise-gcc.c after my change).

Arno