bug#10477: zap-to-char should allow picking from history

[Drew Adams]

> zap-to-char should allow typing e.g., the up arrow to pick a 
> recently used character, and then RET.
> 
> Currently the only way is to type the actual character back in again!
> Even if hard to type CKS!
> 
> Currently one gets 'Non-character input-event'.
> 
> It should work something like one can maneuver at M-x occur's 'List
> lines matching regexp:' prompt.
> So: if a-z etc. is pressed, then no RET should be required.
> 
> If any 'Non-character input-event' is pressed, then we should 
> be able to manipulate from a history list of recently zapped chars.

This sounds similar to bug #1580 (which jidanni also filed), though the emphasis
seems a bit different.

---

FWIW, in Icicles, command `icicle-zap-to-char' uses function
`icicle-read-char-maybe-completing' interactively, which is like `read-char'
unless you hit a completing key (e.g. `TAB') or you hit `C-q'.

If you hit a completing key, you complete a character name against either the
names of your previously entered Unicode chars (default behavior) or all Unicode
char names (depends on an option setting).

It is function `icicle-read-char-by-name', a replacement for
`read-char-by-name', which does the completion.  It also populates the
Unicode-char history list used by `icicle-read-char-maybe-completing'.

You can read (and zap to) a TAB char by hitting C-q first: `C-q TAB'.  You can
read (and zap to) a `C-q' char by hitting `C-q C-q'.

The idea is to try to make it easier to zap to Unicode (e.g. Chinese) chars that
you have already inserted.  The tradeoff is that zapping to a TAB or C-q char
requires you to hit `C-q' first.

(I don't really know whether completing against a char name is necessarily
easier than "to type the actual character back in again".  Completing against a
history list instead of all Unicode chars as candidates, the thought was that it
might be.  Dunno.)