lavc: mark the old audio/video encoding API as deprecated

libavcodec/avcodec.h

@@ -4620,7 +4620,10 @@ AVCodec *avcodec_find_encoder_by_name(const char *name);
  *                            value of got_packet_ptr is undefined and should
  *                            not be used.
  * @return          0 on success, negative error code on failure
+ *
+ * @deprecated use avcodec_send_frame()/avcodec_receive_packet() instead
  */
+attribute_deprecated
 int avcodec_encode_audio2(AVCodecContext *avctx, AVPacket *avpkt,
                           const AVFrame *frame, int *got_packet_ptr);
 
@@ -4656,7 +4659,10 @@ int avcodec_encode_audio2(AVCodecContext *avctx, AVPacket *avpkt,
  *                            value of got_packet_ptr is undefined and should
  *                            not be used.
  * @return          0 on success, negative error code on failure
+ *
+ * @deprecated use avcodec_send_frame()/avcodec_receive_packet() instead
  */
+attribute_deprecated
 int avcodec_encode_video2(AVCodecContext *avctx, AVPacket *avpkt,
                           const AVFrame *frame, int *got_packet_ptr);