lavc: Make AVPacket.duration int64, and deprecate convergence_duration

Note that convergence_duration had another meaning, one which was in
practice never used. The only real use for it was a 64 bit replacement
for the duration field. It's better just to make duration 64 bits, and
to get rid of it.

Signed-off-by: Vittorio Giovara <vittorio.giovara@gmail.com>

libavcodec/audio_frame_queue.c

@@ -111,7 +111,7 @@ int ff_af_queue_add(AudioFrameQueue *afq, const AVFrame *f)
 }
 
 void ff_af_queue_remove(AudioFrameQueue *afq, int nb_samples, int64_t *pts,
-                        int *duration)
+                        int64_t *duration)
 {
     int64_t out_pts = AV_NOPTS_VALUE;
     int removed_samples = 0;