Fix resending file transfer with 'null' file. On cancellation, the filetransfer is not reset that lead the message to have its Content as not isFile().
Then, next call to send() was done with no isFile() in its contents.
- Restore the content.

- Use pt->normal_bitrate only if stream->ms.max_target_bitrate is not set.

Default layout to ActiveSpeaker to ensure backward compatibility as the the server may receive SDP streams with an unknwon content.

Update README.md for iOS compilation, and change the use of INVITE with replaces header, so that we use it only when we are sure that the callee got the first INVITE.
Fix build with tunnel for iOS and MacOS.

Update MainDb version to 1.0.30 to handle compatibility issues when upgrading from release/5.2 to release/5.3

Add setting to disable RTP volumes, because implementaitons that do not ignore RTP extension headers they do not support.

Do not do anything if a participant is added twice to a conference in a very short period of time - even before receiving the 200Ok response of the reINVITE

Fix soundcard sampling rate initialisation, fix non-usage of CallParams's Account property for sip routes.

Fix V4Mapped address sometimes advertised in SDP.

- and fix build options to compile only the requested KEMs
- add  missing ZRTP auth string descriptor

    to:
    - store conference information on the device holding the conference
    - correctly set the organizer by looking at the joining mode. If it is
      FocusOwner, the use it
    - Do not default organizer to me participant
    - Set the role of the me participant of a local conference to speaker

do not compile example plugin for iOS

liblinphone:
Correctly set minimum OS version for Apple devices to example plugin