[ia64-abi] Issue reminder

[Martin von Loewis]

> But, I don't know whether we can do that, in the sense of whether we
> can treat __int64 as a typedef AND then use signed/unsigned prefixes.
> Does anyone know the rules?

This is an extension, so you (we) can do whatever we want. If you want
__int64 to be a full keyword, then specifying that formally is quite
involved. In [basic.fundamental]/2, you'd have a new signed integer
type. That gives you new standard conversion sequences, and so on...

You could say __int64 is a predefined #define.

Or you could say __int64 is a magic alias for 'long long', and should
be treated as 'int' in all places.

Regards,
Martin