[RFC] prototype altivec function overloading rewrite

[Aldy Hernandez]

> I still have to work out how to do the predicates, and to sort out 
> languages other than C, but the rest is already in place.

C++ can be done with real C++ overloading as <altivec.h> already
does.  But if you want to implement an all-encompassing approach, that
would be peachy.  You don't need to worry about anything non C/C++
ish.

> I agree that this would be an abuse of fold_builtin.

Abuse?  AltiVec is in the GCC abuse business.

Aldy