The kernel is used in OS X Mountain Lion or below, or iOS version 8 or
below.

Updates golang/go#17015.

Change-Id: I8a849dc2ab4e04535f893b776bf704079cc91977
Reviewed-on: https://go-review.googlesource.com/33250
Run-TryBot: Mikio Hara <mikioh.mikioh@gmail.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>