[...]
So, essentially, what you found is that all versions you looked at,
did indeed define va_list if <stdarg.h> was included?
essentially I found that all versions define it crtdefs.h
The question is if we want to keep it in vadefs (and then import that
one from crtdefs, which I think is ugly) or define it once in crtdefs.h
and then import crtdefs.h from vadefs.h