Support for multi-stream BZip2

[FabriceBoyer]

When trying to decompress BZ2 wikipedia dumps (https://dumps.wikimedia.org/enwiki/20170101), I reach an unexpected EndOfFile exception

This is apparently linked to the usage of parallel compression when creating the bzip2 file. More informations about this feature and a possible workaround are present at the following link : http://chaosinmotion.com/blog/?p=723

Would it be possible to add this feature to SharpZipLib so we can uncompress these very large files only in memory ?

Regards, Fabrice