We're going to wean off IRC, but as a quick fix, only announce 0-60 seconds
after we see a join, or every 6 hours.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
lightningd now uses a WHOIS query on itself to learn its external IP
address and announces that on the channel with the NODE message. It also
tracks other nodes in the routing table.
Refactored the signature verification to reuse it for both CHAN and NODE
messages.
Added channel announcement serialization and parsing, as well as the
entrypoints for the IRC peer discovery. Announcements are signed by the
sending endpoint and signatures are verified before adding the channels
to the local view of the topology. We do not yet verify the existence of
the anchor transaction.
