FFmpeg: add missing "const" to 3 prototypes

src/FFmpeg.h

@@ -671,12 +671,21 @@ extern "C" {
       (AVFormatContext *s, AVDictionary **options),
       (s, options)
    );
+#if LIBAVFORMAT_VERSION_INT >= AV_VERSION_INT(55, 33, 101)
+   FFMPEG_FUNCTION_WITH_RETURN(
+      AVOutputFormat*,
+      av_oformat_next,
+      (const AVOutputFormat *f),
+      (f)
+   );
+#else
    FFMPEG_FUNCTION_WITH_RETURN(
       AVOutputFormat*,
       av_oformat_next,
       (AVOutputFormat *f),
       (f)
    );
+#endif
    FFMPEG_FUNCTION_WITH_RETURN(
       AVCodec*,
       av_codec_next,
@@ -743,12 +752,21 @@ extern "C" {
       (AVFifoBuffer *f),
       (f)
    );
+#if LIBAVUTIL_VERSION_MAJOR >= 53
+   FFMPEG_FUNCTION_WITH_RETURN(
+      int,
+      av_fifo_size,
+      (const AVFifoBuffer *f),
+      (f)
+   );
+#else
    FFMPEG_FUNCTION_WITH_RETURN(
       int,
       av_fifo_size,
       (AVFifoBuffer *f),
       (f)
    );
+#endif
    FFMPEG_FUNCTION_WITH_RETURN(
       void*,
       av_malloc,
@@ -796,12 +814,21 @@ extern "C" {
       (AVDictionary **m),
       (m)
       );
+#if LIBAVUTIL_VERSION_MAJOR >= 53
+   FFMPEG_FUNCTION_WITH_RETURN(
+      AVDictionaryEntry *,
+      av_dict_get,
+      (const AVDictionary *m, const char *key, const AVDictionaryEntry *prev, int flags),
+      (m, key, prev, flags)
+   );
+#else
    FFMPEG_FUNCTION_WITH_RETURN(
       AVDictionaryEntry *,
       av_dict_get,
       (AVDictionary *m, const char *key, const AVDictionaryEntry *prev, int flags),
       (m, key, prev, flags)
    );
+#endif
    FFMPEG_FUNCTION_WITH_RETURN(
       int,
       av_dict_set,