To be used e.g. in github.com/mdlayher/vsock

Change-Id: I52148a6e6c53c022c07e2cc8bf7348a96445c17b
Reviewed-on: https://go-review.googlesource.com/76193
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matt Layher <mdlayher@gmail.com>