bug#4286: CVS: lisp/ido.el -- improve ido-ignore-files

[Chong Yidong]

> Change against Emacs CVS tree as of 2009-08-29 11:5 UTC
>
> 2009-08-29  Jari Aalto  <jari.aalto@cante.net>
>
>         * ido.el (ido-ignore-files): Add RCS, svn, darcs, sh, git, mtn
>         version control directories.

This change makes sense only if we never want to change these
directories.  In practice, if you are trying to complete a dotfile, you
are already planning to do something funky, so Emacs probably shouldn't
try to do any second-guessing.