Use uint32s instead of int32s where practical, and add an API version
request. Also, try to return all devices added, not just the first,
and box device arguments.
Break up D-Bus into two components: a D-Bus core that can be used by any
part of the server (for the moment, just the D-Bus hotplug API, and the
forthcoming HAL hotplug API), and the old D-Bus hotplug API.