raop: Add autoreconnect feature
This patch adds the autoreconnect feature to the raop module.
This is mainly to be used in a server context, but can be used
also in a desktop usage context.
With autoreconnect feature, the raop module behaves like this:
- At initialisation or in case of the RTSP TCP connection lost, it
tries to reconnect every 5 seconds
- In case of any fatal error, it tries to reconnect every 5 seconds
- In UDP mode, if no timing packets received anymore for a long time,
RTSP connection is closed, then it tries to reconnect..
- After reconnection, once RTSP session has been established again,
playing is resumed automatically.
- When the connection is not established yet (or loss), the sink
behaves like a null sink. In the source code I called it "autonull",
even if autonull is set to autoreconnect param value, it could be
split into two different params.