MINOR: remove the client/server side distinction in SI addresses

Stream interfaces used to distinguish between client and server addresses
because they were previously of different types (sockaddr_storage for the
client, sockaddr_in for the server). This is not the case anymore, and this
distinction is confusing at best and has caused a number of regressions to
be introduced in the process of converting everything to full-ipv6. We can
now remove this and have a much cleaner code.
diff --git a/src/peers.c b/src/peers.c
index bbe99d4..ac24e12 100644
--- a/src/peers.c
+++ b/src/peers.c
@@ -1138,7 +1138,7 @@
 	t->context = s;
 	t->nice = l->nice;
 
-	memcpy(&s->si[1].addr.s.to, &peer->addr, sizeof(s->si[1].addr.s.to));
+	memcpy(&s->si[1].addr.to, &peer->addr, sizeof(s->si[1].addr.to));
 	s->task = t;
 	s->listener = l;