#6 Missing support for zstd archives

[Alan Alberghini]

Hello,

I just recently tried to convert the deb package file for apidash (https://github.com/foss42/apidash/) to a (Slackware) tgz file using alien but I got the following error:

Unknown control member! at /usr/share/perl5/vendor_perl/Alien/Package/Deb.pm line 182

Upon further inspection, I noticed that the deb packages contain data and control archives compressed using zstd (data.tar.zst and control.tar.zst).

This was easily solved by adding two new branches in the get_data_member_cmd and getcontrolfile functions like in the attached patch.