Several fixes for MP4Demuxer

• timescale pass to MP4Remuxer as original (no longer fixed to 1000)
• Support files bigger than 2 GB (co64 box and big mdat box support)
• Pass accurate duration calculated by moov data back to transmuxer controller and update segment timestampBase
• Drop extra data after chunks

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• 时间度量按照原样传递给MP4Remuxer（不再固定为1000）
• 支持大于2GB的文件（支持co64和大的mdat）
• 将moov计算得出的精确时长传回转封装控制器并更新分段时间基数
• 丢弃区块后多余数据

Dec 14, 2017

• Added fix for files no ctts given
• 修复无ctts文件出错