avformat/id3v2: Mark variable as unused to avoid "set but not used" warning

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/id3v2.c

@@ -408,7 +408,7 @@ static void read_comment(AVFormatContext *s, AVIOContext *pb, int taglen,
     const char *key = "comment";
     uint8_t *dst;
     int encoding, dict_flags = AV_DICT_DONT_OVERWRITE | AV_DICT_DONT_STRDUP_VAL;
-    int language;
+    av_unused int language;
 
     if (taglen < 4)
         return;