Add a quality factor packet side data

This is necessary to preserve the quality information currently exported
with coded_frame. Add the new side data to every encoder that needs it,
and use it in avconv.

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

libavformat/dump.c

@@ -359,6 +359,9 @@ static void dump_sidedata(void *ctx, AVStream *st, const char *indent)
             av_log(ctx, AV_LOG_INFO, "audio service type: ");
             dump_audioservicetype(ctx, &sd);
             break;
+        case AV_PKT_DATA_QUALITY_FACTOR:
+            av_log(ctx, AV_LOG_INFO, "quality factor: %d", *(int *)sd.data);
+            break;
         default:
             av_log(ctx, AV_LOG_WARNING,
                    "unknown side data type %d (%d bytes)", sd.type, sd.size);