We remove the unused status_send_fd, and rename status_send_sync (it
should only be used for that case now).
We add a status_setup_async(), and wire things internally to use that
if it's set up: status_setup() is renamed status_setup_sync().
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
We have some duplication in handling queues, so this is an attempt at
deduplicating some of that work. `daemon_conn` now uses the
`msg_queue` and `channeld` was also migrated to `msg_queue`. At the
same time I made `msg_queue` create a copy of the messages or takes
over messages marked with `take()`. This should make cleaning up
messages easier.
This allows us to break out of the normal queue-based write loop and
handle things ourself for a while. Currently this is used to trigger
regular gossip dumps that do not proceed until the buffers have been
cleared in order to avoid memory-explosions.
