bug#13602: 24.3.50; remove bindings for `icomplete-minibuffer-map' - make a separate mode

[Drew Adams]

> > `M-x list- <C-right> <C-right> C-RET'
> 
> So you're voting for C-left/C-right?  OK, noted.

Also not great.  Removes two useful editing keys from the minibuffer
(`backward-word', `forward-word').

But again, if the use of keys is optional and easily toggled, and especially if
it is turned off by default, then it doesn't matter so much which keys you
choose.