line up completions vertically

[jidanni]

You know how it shows us the choices when we hit TAB,
# rm /var/tmp/dan_home_bkp2009-07-26-02-<TAB>
dan_home_bkp2009-07-26-02-18-36.bz2  dan_home_bkp2009-07-26-02-27-07.bz2

Well given that we are not going to bother to make the differing endings
bold, like in emacs, well, at least we can line them up vertically,

dan_home_bkp2009-07-26-02-18-36.bz2
dan_home_bkp2009-07-26-02-27-07.bz2

so the eye can get a better comparison of just where they differ.