readline rl_callback problems

[Adam Luter]

Well I think I fixed the lock up problems (sorry for bothing you about
that).  I didn't think about the file descriptor being changed :) .  So
I moved the fd set lines inside the while loop and now it doesn't
lockup.

Still can't figure out how to avoid the double prompt on ctrl-d; but
that's a much more minor issue.

Thanks!
  Adam Luter