preparing for the syscall package freeze.

««« original CL description
syscall: regenerate z-files for darwin

Updates z-files from 10.7 kernel-based to 10.9 kernel-based.

LGTM=iant
R=golang-codereviews, bradfitz, iant
CC=golang-codereviews
https://golang.org/cl/102610045
»»»

LGTM=r
R=r
CC=golang-codereviews
https://golang.org/cl/114530044