MINOR: protocol: rename the ->bind field to ->listen

The function currently is doing both the bind() and the listen(), so
let's call it ->listen so that the bind() operation can move to another
place.
diff --git a/src/proto_uxst.c b/src/proto_uxst.c
index 6691e85..24ab191 100644
--- a/src/proto_uxst.c
+++ b/src/proto_uxst.c
@@ -56,7 +56,7 @@
 	.l3_addrlen = sizeof(((struct sockaddr_un*)0)->sun_path),/* path len */
 	.accept = &listener_accept,
 	.connect = &uxst_connect_server,
-	.bind = uxst_bind_listener,
+	.listen = uxst_bind_listener,
 	.enable_all = enable_all_listeners,
 	.disable_all = disable_all_listeners,
 	.get_src = sock_get_src,