cmd/ld: don't show cursym in gcc invocation failure message
before:
fmt.statictmp_0731:/usr/local/go/pkg/tool/linux_amd64/6l: running gcc failed: unsuccessful exit status 0x100
now:
/usr/local/go/pkg/tool/linux_amd64/6l: running gcc failed: unsuccessful exit status 0x100

R=golang-dev, iant, r
CC=golang-dev
https://codereview.appspot.com/8827045
doc: fix another broken link

Fixes issue 5316

R=golang-dev, r, minux.ma
CC=golang-dev
https://codereview.appspot.com/8871043
net: enable test for runtime.PollDesc leak

Update issue 5219.

R=golang-dev, dvyukov, r
CC=golang-dev
https://codereview.appspot.com/8602047
cmd/ld: do not relocate ignored PE sections

This should have been part of CL8715043.

Update issue 5106

R=golang-dev, r, iant
CC=golang-dev
https://codereview.appspot.com/8676050