[RFA] Fix float argument passing in inferior function calls for ppc64

[Mark Kettenis]

> From: Thiago Jung Bauermann <bauerman@br.ibm.com>
> Date: Tue, 15 Jan 2008 18:33:54 -0200
> 
> On Tue, 2008-01-15 at 15:39 -0200, Thiago Jung Bauermann wrote:
> > > Is the first word used for anything in the new ABI?  If not, you could
> > > support both ABIs by copying the value into both the first and the
> > > second word.
> > 
> > Great idea. I will resend the patch using that approach then.
> 
> What about this patch?

Looks fine to me, but I have no means to test it.