adding vttC box parsing
adding vttC box parsing

cconcolato/mp4box.js,sjames1958gm/mp4box.js,hanzeil/mp4box.js,sjames1958gm/mp4box.js,cconcolato/mp4box.js,b123400/mp4box.js,b123400/mp4box.js,gpac/mp4box.js,hanzeil/mp4box.js,gpac/mp4box.js