net: fix windows build

R=golang-dev, r2
CC=golang-dev
https://golang.org/cl/4184051

src/pkg/net/multicast_test.go

@@ -5,10 +5,14 @@
 package net
 
 import (
+	"runtime"
 	"testing"
 )
 
 func TestMulticastJoinAndLeave(t *testing.T) {
+	if runtime.GOOS == "windows" {
+		return
+	}
 	addr := &UDPAddr{
 		IP:   IPv4zero,
 		Port: 0,

src/pkg/syscall/syscall_windows.go

@@ -703,7 +703,18 @@ type Linger struct {
 	Linger int32
 }
 
+const (
+	IP_ADD_MEMBERSHIP = iota
+	IP_DROP_MEMBERSHIP
+)
+
+type IpMreq struct {
+	Multiaddr [4]byte /* in_addr */
+	Interface [4]byte /* in_addr */
+}
+
 func SetsockoptLinger(fd, level, opt int, l *Linger) (errno int)    { return EWINDOWS }
+func SetsockoptIpMreq(fd, level, opt int, mreq *IpMreq) (errno int) { return EWINDOWS }
 func BindToDevice(fd int, device string) (errno int)                { return EWINDOWS }
 
 // TODO(brainman): fix all needed for os