hot stuff:
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* do not abort() when no matching codecs !
* finish video support
* stun support
* run a user given command upon incoming calls
* port to eXosip2 to have the following functionnalities:
	* support for incoming sip re-invites
	* support for incoming invites without SDP

low priority:
-------------

* zeroconf support for advertising services (cool stuff!)
* improve sipomatic so that it can record and replay messages.
* have the possibility to define several profiles (config files) and switch between them
* add a vtable entry to notify the application about registration status
