RFC: Add getcpu wrapper

[Zack Weinberg]

On Wed, Dec 5, 2018 at 10:49 AM Florian Weimer <fweimer@redhat.com> wrote:
>
> Ah, so you want to pass a non-null second argument to getcpu?
>
> I think we can expose getcpu (with two arguments), under that name.  Add
> it to <sched.h> or <unistd.h>; I do not have a strong preference.

What's the third argument for?  Is there a concrete reason not to
expose it as well?

zw