- selective extraction, possibly with wildcards

- rename old file to flle~ rather than overwriting

- implement a few unzip/arc style options:
  -a = convert text files (Atari EOL => UNIX NL), -aa = all files
  -e = extract (already the default action)
  -t = test checksums
  -k = keep trailing dot for extensionless filenames
  -l = list (filenames only)
  -L = lowercase filenames
  -d <dir> = set output dir (create if needed)
  -o = overwrite (do not create file~ backups)
  -p = extract to stdout
  -x <pattern> = do not extract files matching pattern
  -v = verbose list

- reverse-engineer the ALF14.COM binary, so we have a compressor.
  this would be more of "just to say I did it" thing, there's no real
  need for it.