Add a new socket for audio stream

When audio is enabled, open a new socket to send the audio stream from
the device to the client.

PR #3757 <https://github.com/Genymobile/scrcpy/pull/3757>

Co-authored-by: Romain Vimont <rom@rom1v.com>
Signed-off-by: Romain Vimont <rom@rom1v.com>

app/src/server.h

@@ -70,6 +70,7 @@ struct sc_server {
     struct sc_adb_tunnel tunnel;
 
     sc_socket video_socket;
+    sc_socket audio_socket;
     sc_socket control_socket;
 
     const struct sc_server_callbacks *cbs;