This makes gcimporter15 build against Go 1.5. Change-Id: I14e7ff80b28d99f996abc19a0a74b08e5e1bbd75 Reviewed-on: https://go-review.googlesource.com/18771 Run-TryBot: Robert Griesemer <gri@golang.org> Reviewed-by: Alan Donovan <adonovan@google.com>