Update vendor (#1498)

vendor/golang.org/x/sys/unix/syscall_freebsd.go

@@ -126,6 +126,15 @@ func SetsockoptIPMreqn(fd, level, opt int, mreq *IPMreqn) (err error) {
 	return setsockopt(fd, level, opt, unsafe.Pointer(mreq), unsafe.Sizeof(*mreq))
 }
 
+// GetsockoptXucred is a getsockopt wrapper that returns an Xucred struct.
+// The usual level and opt are SOL_LOCAL and LOCAL_PEERCRED, respectively.
+func GetsockoptXucred(fd, level, opt int) (*Xucred, error) {
+	x := new(Xucred)
+	vallen := _Socklen(SizeofXucred)
+	err := getsockopt(fd, level, opt, unsafe.Pointer(x), &vallen)
+	return x, err
+}
+
 func Accept4(fd, flags int) (nfd int, sa Sockaddr, err error) {
 	var rsa RawSockaddrAny
 	var len _Socklen = SizeofSockaddrAny