Support skipping non-void gerbage data

[at-wat]

https://github.com/Matroska-Org/matroska-test-files#4-live-stream-recording
Official test data test4.mkv contains 0A0A0A0A... in Segment Element.

https://lists.matroska.org/pipermail/matroska-devel/2015-December/004918.html (not answered)

ref: #84

[at-wat]

Seems that invalid element should be skipped byte by byte.