+S4U:
+ - Barrier::wait returns SG_BARRIER_SERIAL_THREAD for (only) one actor
+ for consistency with pthread_barrier_wait()
+ - Host::get_englobing_zone() returns the englobing netzone
+ - Actor::on_destruction is now called in the destructor
+ Actor::on_termination new signal called when the actor terminates
+ its code.
+ - Global signals are now part of the Engine:
+ - on_platform_creation: after config settings, before the XML parsing
+ - on_platform_created: right after the XML parsing
+ - on_time_advance: each time the clock advances
+ - on_simulation_end: after simulation, before cleanups
+ - on_deadlock: as the name implies.
+ - C bindings:
+ - sg_{actor,host,link}_{data,data_set}() now all exist.
+ Use them to attach user data to the object and retrieve it.
+