vendor: Update golang.org/x/net/...

vendor/golang.org/x/net/ipv6/sys_windows.go

@@ -23,7 +23,9 @@ const (
 
 	sysSizeofSockaddrInet6 = 0x1c
 
-	sysSizeofIPv6Mreq = 0x14
+	sysSizeofIPv6Mreq     = 0x14
+	sysSizeofIPv6Mtuinfo  = 0x20
+	sysSizeofICMPv6Filter = 0
 )
 
 type sysSockaddrInet6 struct {
@@ -39,6 +41,15 @@ type sysIPv6Mreq struct {
 	Interface uint32
 }
 
+type sysIPv6Mtuinfo struct {
+	Addr sysSockaddrInet6
+	Mtu  uint32
+}
+
+type sysICMPv6Filter struct {
+	// TODO(mikio): implement this
+}
+
 var (
 	ctlOpts = [ctlMax]ctlOpt{}