lnwire: add BOLT#2 channel reestablish message

In this commit the reestablish message have been added, which serves as
channel state synchronization message. Before exchanging the messages
for particular channel peers have to send it to each other as the
first message in order to be sure that non of the updates have been
lost because of the previous disconnect.

lnwire/message.go

@@ -40,6 +40,7 @@ const (
 	MsgCommitSig                           = 132
 	MsgRevokeAndAck                        = 133
 	MsgUpdateFailMalformedHTLC             = 135
+	MsgChannelReestablish                    = 136
 	MsgUpdateFee                           = 137
 	MsgChannelAnnouncement                 = 256
 	MsgNodeAnnouncement                    = 257
@@ -78,6 +79,8 @@ func (t MessageType) String() string {
 		return "RevokeAndAck"
 	case MsgUpdateFailMalformedHTLC:
 		return "UpdateFailMalformedHTLC"
+	case MsgChannelReestablish:
+		return "ChannelReestablish"
 	case MsgError:
 		return "Error"
 	case MsgChannelAnnouncement:
@@ -169,6 +172,8 @@ func makeEmptyMessage(msgType MessageType) (Message, error) {
 		msg = &UpdateFee{}
 	case MsgUpdateFailMalformedHTLC:
 		msg = &UpdateFailMalformedHTLC{}
+	case MsgChannelReestablish:
+		msg = &ChannelReestablish{}
 	case MsgError:
 		msg = &Error{}
 	case MsgChannelAnnouncement: