Add atool package

A set ot tools for managing file archives of various types (tar,
tar+gzip, zip etc).

aunpack: extracts  files from an archive
apack: creates archives (or compresses files). If no file arguments are
specified, filenames to add are read from standard in.
als: lists files in an archive
acat: extracts files in an archive to standard out
adiff: generates a diff between two archives
arepack: repacks archives to a different format