Uncompressing .gz and .bz2 files when using SevenZipSharpLib with a 7z.dll of version 16.04 or greater.

[CraigScape]

I ran into an issue uncompressing .gz and .bz2 files when using SevenZipSharpLib with a 7z.dll of version 16.04 or greater. These files would uncompress just fine using 7z.dll version 9.20.

After some time debugging the issue I found that the ArchiveExtractCallback.SetTotal() function is not being called when using the newer 7z.dll.

This results in _bytesCount being 0 when ArchiveExtractCallback.IntEventArgsHandler() is called. This results in a divide by zero error which the user sees as "The execution has failed due to the bug in the SevenZipSharp.".

I was able to work around this issue with the following code change in ArchiveExtractCallback.IntEventArgsHandler():

		FROM:
        var pold = (int)((_bytesWrittenOld * 100) / _bytesCount);
        _bytesWritten += e.Value;
        var pnow = (int)((_bytesWritten * 100) / _bytesCount);

		TO:

        var pold = (int)((_bytesWrittenOld * 100) / Math.Max(_bytesCount, 1));
        _bytesWritten += e.Value;
        var pnow = (int)((_bytesWritten * 100) / Math.Max(_bytesCount, 1));

This only fixes the divide by zero error, the real fix would require properly getting the uncompressed file size prior to the extraction.