- regc refresh automatically
- if dialog CANCEL return 481, disconnect the dialog
- presence implement callback from event_sub
- presence supports multiple tuples!
- implement event headers!

Prio Task
 10  General authentication framework in pjsua.
 10  Start on SUBSCRIBE/NOTIFY framework.
 10  Refactor pjsip_event
---
 10  Concurrency in pool factory because endpt pool is shared by app.
     Choices:
	- another pool factory (thread safe) for app ==> waste memory.
	- endpt pool is thread safe ==> slow
 10  Sound in Linux
 10  Support TCP
 10  Per instance configuration:
		- max number of tsxs
		- max number of dialogs
		- socket buffer size