This is an internal type: it has no API guarantees (indeed, I'm about
to change it, which is how I discovered scb was using it).
Fortunately for every case we care about, it is actually a wireaddr
(in theory the peer can connect locally using a local socket, but this
is mostly for testing and is a very strange setup, and so simply don't
do scb for those).
In this case, the wire encoding is a single byte followed by the
wireaddr, so open-code that in scb_wire.csv for compatibility.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>