This commits adds a missing syscall and a missing structure in syscall
package.

Change-Id: I9d630454c56337267f7bbb023e601246e14fc929
Reviewed-on: https://go-review.googlesource.com/c/163978
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>