bug#13092: 24.3.50; regression: `icomplete-mode' does not echo key bindings

[Drew Adams]

> > Could you give me a recipe that might show the problem?
> 
> M-x icomplete-mode RET
> C-x b left-char RET RET
> C-x b RET
> C-x b left-char
> 
> The first left-char does not output the key-binding (because the
> code is only triggered for matches), but the second does (in 24.3).

Got it.  Thx.  Yes, same thing with Icomplete+: key <left> is echoed.

Personally, this (rare, I would guess) minor nuisance is outweighed
by the positive help provided by showing keys for sole-match commands.

As a different user, you might feel differently about the relative
value.

The important thing is that if you restore this fine feature then
you simply give individual _users_ the choice: there was already a
user option for whether to show key bindings,
`icomplete-show-key-bindings'.  Restoring that option is of course
part of fixing the regression.