net: deflake raw IP protocol entry test on Windows

Update issue 5344

R=golang-dev, dave, r, alex.brainman
CC=golang-dev
https://codereview.appspot.com/8934043
runtime: prevent the GC from seeing the content of a frame in runfinq()

Fixes issue 5348.

R=golang-dev, dvyukov
CC=golang-dev
https://codereview.appspot.com/8954044
undo CL 8954044 / ad3c2ffb16d7

It works on i386, but fails on amd64 and arm.

««« original CL description
runtime: prevent the GC from seeing the content of a frame in runfinq()

Fixes issue 5348.

R=golang-dev, dvyukov
CC=golang-dev
https://codereview.appspot.com/8954044
»»»

R=golang-dev, r
CC=golang-dev
https://codereview.appspot.com/8695051
cmd/gc: initialize t->width in dgcsym() if required

Update issue 5291.

R=golang-dev, daniel.morsing, iant, r
CC=golang-dev
https://codereview.appspot.com/8663052