[Patch] Altivec ABI as default for powerpc64 linux

[Hartmut Penner]

> >          We are not proposing enabling Altivec by default, but enabling
> > Altivec ABI by default.  This ensures that stack alignment is correct
and
> > varargs are passed in the correct registers for Altivec applications to
> > interoperate seemlessly with non-Altivec libraries, etc.

> It also means you can't pass vector parameters, since they'd have to
> go in vector registers and your chip doesn't have any, correct?

The varargs implementation work without vector register, since unnamed args
are passed on the stack. For example, we have a vfprintf implementation for
glibc supporting vector types (%v), which is compiled with
-mabi=altivec only, therefore containing no altivec instruction.
      regards, Hartmut