- categorize diagnostics as fatal or warning.

- include some of Alfred's email commentary in the doc dir.

- create some alf archives and hexedit them to introduce errors, make
  sure unalf doesn't segfault or get stuck in a loop (it should
  *always* exit cleanly).

- reverse-engineer the LZ.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. alternatively, see if I can rewrite the compressor
  in C.