Fix opening 7z files created by apache commons compress#74

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cielavenir wants to merge 3 commits intofancycode:masterfrom

cielavenir:fixcommons

Commits on Aug 12, 2020

fixed reading packed stream crc, fixing 7z reading written by apache commons compress
cielavenir
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substreamsinfo crc might not be provided
cielavenir
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Commits on Aug 13, 2020

Fix _read64Bit when leading byte is 0xff
cielavenir
committed