tasks ice-9 ftw

[Kevin Ryde]

I added an entry to the tasks file,

  - ice-9/ftw.scm problems:
    - stat-dir-readable?-proc decides the readability of a directory
      by looking at "stat" information, but does so imperfectly.  It
      doesn't take into account supplementary group memberships
      (getgroups), or that "root" can read anything, or access control
      lists (on systems which have those).  Just attempting an opendir
      would be simpler and more reliable.
    - visited?-proc tests only stat:ino, but this is not unique across
      filesystems, stat:dev must be used too.
    - Passing "/" to start from the root directory doesn't work, it
      looks like perhaps trailing slashes are stripped too agressively.

I put it under 1.8, anyone who disagrees with that severity can move
it.  Clean fixes could no doubt go into the 1.6 branch for instance,
but I'm not feeling brave enough to attack it at the moment.