[dev.power64] all: merge default (dd5014ed9b01) into dev.power64

Still passes on amd64.

LGTM=austin
R=austin
CC=golang-codereviews
https://golang.org/cl/165110043

diff --cc src/cmd/gc/walk.c
Simple merge

diff --cc src/runtime/asm_386.s
Simple merge

diff --cc src/runtime/asm_amd64.s
Simple merge

diff --cc src/runtime/asm_arm.s
Simple merge

diff --cc src/runtime/mgc0.c
Simple merge

diff --cc src/runtime/proc.c
Simple merge

diff --cc src/runtime/runtime.c
Simple merge

diff --cc src/runtime/sys_nacl_amd64p32.s
Simple merge