Things that would be nice but aren't really necessary:

0.  Update the documentation.

1.  Properly handle commands like `man 3f intro' when the name of the
    file we want is something like .../man3/intro.3f.  The way this is
    done right now seems sort of kludgey but it mostly works.  See
    man.c for details.

2.  Malloc everything instead of having fixed limits... Or at least
    check the limits everywhere.  If you're paranoid about this, make
    the limits big (famous last words: really, there aren't that many
    things that could go wrong :-).

3.  Try to do a little better job of memory management.  There are a
    lot of little temporary strings that are malloc'd and never freed.
    This is probably ok for a standalone program but not so good if
    you wanted to call man() from another program.