[release-branch.go1.3] net: prevent spurious on-connect events via epoll on linux

««« CL 120820043 / 06a4b59c1393
net: prevent spurious on-connect events via epoll on linux

On Linux, adding a socket descriptor to epoll instance before getting
the EINPROGRESS return value from connect system call could be a root
cause of spurious on-connect events.

See golang.org/issue/8276, golang.org/issue/8426 for further information.

All credit to Jason Eggleston <jason@eggnet.com>

Fixes issue 8276.
Fixes issue 8426.

LGTM=dvyukov
R=dvyukov, golang-codereviews, adg, dave, iant, alex.brainman
CC=golang-codereviews
https://codereview.appspot.com/120820043
»»»

TBR=r, rsc
CC=golang-codereviews
https://codereview.appspot.com/128110045
[release-branch.go1.3] runtime: fix GC bitmap corruption

««« CL 103640044 / d2f256096d8d
runtime: fix GC bitmap corruption
Fixes issue 8299.

R=golang-codereviews
CC=golang-codereviews, khr, rsc
https://codereview.appspot.com/103640044
»»»

TBR=r, rsc
CC=golang-codereviews
https://codereview.appspot.com/125150044