Patch to iswitchb.el from 21.1

[Christopher S. Kush]

On the following page is a patch for iswitchb.el to allow the
user to Customize what happens when buffer name completion
fails.

-- 
   "One does not wait for (X)Emacs to load,
    one jumps up and down with excitement."
                   -- Henrik Enberg


273a274,281
> (defcustom iswitchb-cannot-complete-hook 'iswitchb-completion-help
>   "*Hook run when `iswitchb-complete' can't complete any more.
> The most useful values are `iswitchb-completion-help', which pops up a
> window with completion alternatives, or `iswitchb-next-match' or
> `iswitchb-prev-match', which cycle the buffer list."
>   :type 'hook
>   :group 'iswitchb)
> 
635c643
<          (iswitchb-completion-help))
---
>          (run-hooks 'iswitchb-cannot-complete-hook))
652c660
<            (iswitchb-completion-help)
---
>              (run-hooks 'iswitchb-cannot-complete-hook)