decoder/ogg: need to sync small files while looking for EOS

When calling OggSeekFindEOS() from inside a OggVisitor callback, then
the #InputStream may be in the middle of an Ogg packet, and the newly
initialized #ogg_sync_state will not be able to load it without the
help of ogg_sync_pageseek().  By passing "synced=false" to
OggSeekFindEOS(), we force the use of ogg_sync_pageseek() even when
not actually seeking.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/719

src/decoder/plugins/OggDecoder.cxx

@@ -47,8 +47,12 @@ OggDecoder::LoadEndPacket(ogg_packet &packet) const
 		DecoderReader reader(client, input_stream);
 		OggSyncState sync2(reader);
 		OggStreamState stream2(GetSerialNo());
+
+		/* passing synced=false because we're inside an
+		   OggVisitor callback, and our InputStream may be in
+		   the middle of an Ogg packet */
 		result = OggSeekFindEOS(sync2, stream2, packet,
-					input_stream);
+					input_stream, false);
 	}
 
 	/* restore the previous file position */