runtime: fix freebsd arm for hash change
runtime: fix freebsd arm for hash change

Was missing definitions of open, read, close.

R=golang-dev
CC=golang-dev
https://codereview.appspot.com/7828043

h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang