fixup! X on msgpack support

This fixes a stucked client: now the handshake packet is correctly
proceeded.

go/neo/neonet/newlink.go

@@ -276,17 +276,13 @@ func rxHello(errctx string, rx *xbufReader) (enc proto.Encoding, version uint32,
 		if err != nil {
 			return 0, 0, err
 		}
-		if !bytes.Equal(b[4:], []byte{'O', 0}) {
+		if !bytes.Equal(b[4:5], []byte{'O'}) {
 			badMagic = true
 			break
 		}
 
 		peerEnc = 'M'
-		rxM := msgp.Reader{R: rx.Reader}
-		peerVer, err = rxM.ReadUint32()
-		if err != nil {
-			return 0, 0, fmt.Errorf("M: recv peer version: %s", err) // XXX + "read magic" ctx
-		}
+		peerVer = uint32(b[5])
 
 	default:
 		badMagic = true