api: update go1.1, except and next.txt with constant values

O_SYNC changes only on linux-arm (and linux-arm-cgo), but
changes to match O_SYNC on linux-{386,amd64} and what Linux
upstream now uses.  See discussion and links on
https://golang.org/cl/13261050/

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/13575045