Fix build problem for older ffmpeg versions

Fix a build failure for older ffmpeg versions. avcodec_decode_audio4
was deprecated in libavcodec 57.106.100, not 57.12.100, so the
version has been corrected.

Signed-off-by: aneejit1 <aneejit1@gmail.com>

akode/plugins/ffmpeg_decoder/ffmpeg_decoder.cpp

@@ -378,7 +378,7 @@ retry:
     }
     int decoded;
 
-#if LIBAVCODEC_VERSION_INT >= AV_VERSION_INT(57, 12, 100)
+#if LIBAVCODEC_VERSION_INT >= AV_VERSION_INT(57, 106, 100)
     int len = avcodec_receive_frame(d->audioStream_ctx, decodeFrame);
     if (len == 0) {
         decoded = 1;