* dbus/dbus-message.c (struct DBusMessage): put the locked bit and
	the "char byte_order" next to each other to save 4 bytes
	(dbus_message_new_empty_header): reduce preallocation, since the
	message cache should achieve a similar effect
	(dbus_message_cache_or_finalize, dbus_message_get_cached): add a
	message cache that keeps a few DBusMessage around in a pool,
	another 8% speedup or so.

	* dbus/dbus-dataslot.c (_dbus_data_slot_list_clear): new function