[dev.garbage] all: merge dev.power64 (5ad5e85cfb99) into dev.garbage

The goal here is to get the big-endian fixes so that
in some upcoming code movement for write barriers
I don't make them unmergeable.

LGTM=rlh
R=rlh
CC=golang-codereviews
https://golang.org/cl/166890043

diff --cc lib/codereview/codereview.py
Simple merge

diff --cc src/runtime/gcinfo_test.go
Simple merge

diff --cc src/runtime/malloc.go
Simple merge

diff --cc src/runtime/mgc0.c
index bcc5a2f39dd4f3bb3ed8366968456de6ee5ec6a6,e5b6870c668d8a5887d9924a928aee7277a2b05c..f76d7c05cab1d99d40bc997776f4318b3b08892d
--- 1/src/runtime/mgc0.c
--- 2/src/runtime/mgc0.c
+++ b/src/runtime/mgc0.c
@@@ -2065,6 -1802,7 +2065,7 @@@ runtime·unrollgcprog_m(void
                        prog = (byte*)typ->gc[1];
                        unrollgcprog1(mask, prog, &pos, false, true);
                }
 -              
++
                // atomic way to say mask[0] = 1
                x = *(uintptr*)mask;
                ((byte*)&x)[0] = 1;

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