use odd value for new field, to support downgradability

Author: marctyndel

lightning/src/events/mod.rs

@@ -830,7 +830,7 @@ impl Writeable for Event {
 					(1, prev_channel_id, option),
 					(2, claim_from_onchain_tx, required),
 					(3, next_channel_id, option),
-					(4, amount_forwarded_msat, option),
+					(5, amount_forwarded_msat, option),
 				});
 			},
 			&Event::ChannelClosed { ref channel_id, ref user_channel_id, ref reason } => {