log: ability to log struct rval.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

daemon/log.c

@@ -326,7 +326,8 @@ static char *to_string_(const tal_t *ctx,
 			    h->src ? to_string(ctx, lr, struct pubkey,
 					       h->src->peer->id)
 			    : "local");
-	}
+	} else if (streq(structname, "struct rval"))
+		s = tal_hexstr(ctx, u.rval, sizeof(*u.rval));
 
 	return s;
 }

daemon/log.h

@@ -71,6 +71,7 @@ union loggable_structs {
 	const struct abs_locktime *abs_locktime;
 	const struct bitcoin_tx *bitcoin_tx;
 	const struct htlc *htlc;
+	const struct rval *rval;
 	const char *charp_;
 };