- Override main() to instantiate a Main Loop.
- Add Info.plist to liblinphonetester to get video permissions if needed

This work required a major internal refactoring of how streams (audio, video, text, maybe others in the future) are handled by liblinphone.
This refactoring introduces a new design, where a streams are managed through a common base class named 'Stream', by a new class StreamsGroup that has the responsability of coordinating streams together.
In addition, these classes are provided with an OfferAnswerContext, that contains a representation of SDP local parameters, remote parameters, and agreed parameters.

The IceAgent has been redesigned too, renamed as IceService. It is now invoked by the StreamsGroup, and given the same OfferAnswerContext.
The IceService now supports handling of several IP addresses, using getifaddrs() (linux, android, iOS, Mac), windows to be done. The new code is more compact.

The internal function sal_stream_description_active() has been removed as its name was confusing.
Instead sal_stream_description_active() can be used to know if a stream is active (ie port number not zero and no a=bundle-only).

This option makes the creation of 'package_source' custom target optional,
allowing to build with CMake < 3.11 if it is disabled (default).

(cherry picked from commit 141ea279)

Move license to GPLv3, update version number to 4.3.0.

François Grisez authored 6 years ago and DanmeiChen committed 6 years ago

(cherry picked from commit 60031cdc)

(cherry picked from commit 3cdb4644)

(cherry picked from commit 7ffd7a93)