[Issue 21974] ImportC: support __builtin_va_list, __builtin_va_start, __builtin_va_arg, __builtin_va_end

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=21974

Walter Bright <bugzilla at digitalmars.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|importC: Error: undefined   |ImportC: support
                   |identifier                  |__builtin_va_list,
                   |'__builtin_va_list'         |__builtin_va_start,
                   |                            |__builtin_va_arg,
                   |                            |__builtin_va_end

--