Bugfixes for large 7z files (dealing with multiple sections and int overflow)

[igvk]

There a 3 bugfixes here:

• The 2 places I found that have integer value overflow (!) leading to incorrect processing of large archives.
• Not setting stream id leading to incorrect processing of archives with several sections
• There are files created by 7zip with directory entries, that could simply be ignored instead of throwing an exception