- clients will unsubscribe and re-subscribe to the server to force a full state
- servers will send full state to make sure clients are on the same page

If the client receives a partial notify for an unknown participant device, then he will send a subscribe to the server to clear things up

Improve tests:
- verify behaviour when participants are added in a quick succession to remote conference
- improve chat room test coverage

free audio resource before new incoming call, to ensure there is only one write card and avoid crash ios

(cherry picked from commit 76b86a22)

Use sal_get_random_token_lowercase in tests to ensure username compatibility with FlexiAPI validation restrictions

Fix sip address table creation when database connection string containts utf8mb4 as charset, on mariadb 5.5 (mitigates Exception while creating or updating the database's schema : Specified key was too long; max key length is 767 bytes while executing)
Added warning comments in case utf8mb4 varchar columns > 255 were to be indexed

(cherry picked from commit 8b3275e7)

This saves time to establish the audio stream.
Starting before ICE verified was not a good idea: it will trigger retransmissions, and retransmission interval growing over time makes the handshake slower.
Also, fix an issue where callee sets host candidates as default candidates in SDP, sflrx must be preferred.

Look if me is focus to kow whether conference is local or remote

This reverts commit 76651156.

Revert "MagicSearch for case insensitive : replace tolower by regex in order to work without locale."

This reverts commit 3b89c845.

Fixed crash in Android AudioHelper when trying to set looping property of ringtone on devices older than 9.0

Log messages were passed, unchecked, to the log_message_written callback

On Xamarin this callback is written in C#. So the const char* is
converted to a .NET string, which is stored as UTF16. Mono checks for
validity and throws an exception when the string contains illegal byte
sequences, leading to a crash.

Interestingly, though, I was unable to reproduce the crash on UWP, which
uses the .NET Core runtime. The illegal bytes seem to be silently
replaced with the replacement character ('�') without throwing.