Split admin initialization into:
* setting up internal data structures, which is `a_init' as before;
* establishing the daemonic signal handlers, which is now `a_signals';
* creating the admin socket and listening for incoming connections,
which is now `a_listen'; and
* switching alert reporting over to admin clients rather than stderr,
which is now `a_switcherr'.
Given that `a_listen' now need not actually be called, only unlink the
socket object if we actually created it.
Split peer initialization into:
* setting up the data structures, which is `p_init' as before; and
* creating the UDP sockets for communicating with other peers, which
is now `p_bind'.
This will make sense in context.
squash! server/: Split peer and admin initialization into smaller pieces.
server/admin.c: Split out signal-handler establishment.