sflphone-common -> daemon
sflphone-client-gnome -> gnome
sflphone-client-kde -> kde
sflphone-plugins -> plugins

decoder takes the size of encoded buffer and returns number of samples
encoder takes the maximum size of output buffer and returns compressed size
(it assumes we will encode only one frame at a time)

This lead to a dead-lock in its destructor. Instead, AudioRtpFactory
must delete it.

This avoids out of order deallocation issues

Now AudioZrtpSession and AudioSymmetricRtpSession are derived from it, and AudioSrtpSession is derived from AudioSymmetricRtpSession
AudioRtpSession class keeps a pointer to the RTPDataQueue and Thread casts of the 2 specialized classes to access a few, because AudioRtpSession doesn't derive from RTPDataQueue or Thread directly.

_ca is set in constructor and never modified