Monkey's Audio uses subframes too, declare that in its capabilities

Originally committed as revision 19883 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/apedec.c

@@ -901,5 +901,6 @@ AVCodec ape_decoder = {
     NULL,
     ape_decode_close,
     ape_decode_frame,
+    .capabilities = CODEC_CAP_SUBFRAMES,
     .long_name = NULL_IF_CONFIG_SMALL("Monkey's Audio"),
 };