Fix av_dlog invocations with wrong or missing logging context.

This fixes build failures with -DDEBUG in CPPFLAGS.

libavcodec/flashsvenc.c

@@ -176,7 +176,7 @@ static int encode_bitstream(FlashSVContext *s, AVFrame *p, uint8_t *buf,
 
                 bytestream_put_be16(&ptr, zsize);
                 buf_pos += zsize + 2;
-                av_dlog(avctx, "buf_pos = %d\n", buf_pos);
+                av_dlog(s->avctx, "buf_pos = %d\n", buf_pos);
             } else {
                 pred_blocks++;
                 bytestream_put_be16(&ptr, 0);

libavformat/mpegts.c

@@ -1409,7 +1409,7 @@ static int handle_packets(MpegTSContext *ts, int nb_packets)
 
     if (avio_tell(s->pb) != ts->last_pos) {
         int i;
-        av_dlog("Skipping after seek\n");
+        av_dlog(ts->stream, "Skipping after seek\n");
         /* seek detected, flush pes buffer */
         for (i = 0; i < NB_PID_MAX; i++) {
             if (ts->pids[i]) {