windows: implement GetsockoptInt
windows: implement GetsockoptInt

Change-Id: If0b17ccaba5c5d1e07499c222eb3f4c45a094636
GitHub-Last-Rev: a0fb2fc43d8458a0eed024012018ff1e3070b9bf
GitHub-Pull-Request: golang/sys#70
Reviewed-on: https://go-review.googlesource.com/c/sys/+/233200
Run-TryBot: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>

golang/sys,multiplay/golang-sys,multiplay/golang-sys,multiplay/golang-sys,golang/sys,golang/sys,multiplay/golang-sys