avcodec/gifdec: set .caps_internal

libavcodec/gifdec.c

@@ -561,5 +561,7 @@ AVCodec ff_gif_decoder = {
     .close          = gif_decode_close,
     .decode         = gif_decode_frame,
     .capabilities   = AV_CODEC_CAP_DR1,
+    .caps_internal  = FF_CODEC_CAP_INIT_THREADSAFE |
+                      FF_CODEC_CAP_INIT_CLEANUP,
     .priv_class     = &decoder_class,
 };