media_localip is guessed from signaling using call->dest_proxy. This ease the use of liblinphone on a machine with two interfaces (typically a one being a vpn).
Clean things around sal.c and sal_impl.c

Also, the RTP sockets are now always IPv6 when ipv6 is enabled in LinphoneCore,
independently of what is finally proposed in SDP, so that these sockets can always send and recv
with both versions.
This is consistent with what is already done in belle-sip for SIP sockets.

implicit avpf bugfixes: do not configure encoders to use avpf if avpf is not accepted or offered by remote.

- start ZRTP on incoming zrtp-hash even when not selected locally

- ZRTP engine is always initialised even when not selected

make sure in case of SRTP DTLS enabled, ice reinvite is disabled & mandatory encryption is activated

-AVP implicit to AVP implicit calls now using RTCP feedback packets.
-Fixing bugs in call_tester.c

Added boolean parameter implicit_rtcp_fb in LinphoneCallParams and SalStreamDescription  to enable or disable the forcing of AVPF messages feature in AVP.
By default, the feature is enabled and RTCP feedback messages PLI, SLI, RPSI and FIR are supported.

A change in ICE credentials in the SDP detects an ICE restart and triggers stream reconstruction.

Do not use anymore nb_streams but SAL_MEDIA_DESCRIPTION_MAX_STREAMS and skip inactive ones because active streams won't be at the start of the array anymore

fix bugs in Paused state management. It was possible to transition from Paused to PausedByRemote, which actually breaks the Paused state, and eventually allows the pauser to be resumed by the paused.

change the way payload type numbers are assigned, so that an application can support more payload type than the RTP profile table allows to contain.
Compliance with RFC3264 (offer answer model) is improved, by reusing numbers in case of reINVITEs.
Fix memory leaks
Move offer/answer related tests into a new test suite.

refine conditions for refusing an UPDATE