matroska-demux: support matroska demux svp
original matroska-demux can not supoort secure webm container. so add some functions to support extract information about secure content, and protection event.
(cherry picked from commit d66c01db)
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original matroska-demux can not supoort secure webm container. so add some functions to support extract information about secure content, and protection event.
(cherry picked from commit d66c01db)