Make update_local_channel use a timer if it's too soon to make another
update.
1. Implement cupdate_different() which compares two updates.
2. make update_local_channel() take a single arg for timer usage.
3. Set timestamp of non-disable update back 5 minutes, so we can
always generate a disable update if we need to.
4. Make update_local_channel() itself do the "unchanged update" suppression.
gossipd: clean up local channel updates.
5. Keep pointer to the current timer so we override any old updates with
a new one, to avoid a race.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Rusty Russell
0bab2580fc