* introduce new notion of subsystem in addition to signal number
* no need for bitmasks of 'areas' (aka subsystems)
* pass subsystem/signal_nr/... per argument rather than by data structure
This will be used for generic registration and dispatching
of any kind of event. We will have different areas (like
with the debug interface) and each layer can define their
own struct for the event message... This is not tested yet
Harald Welte
Holger Freyther