bug#23325: 25.0.92; insert-char: cannot find all chars if input is unicode name

[Eli Zaretskii <eliz@gnu.org>]

> Date: Thu, 21 Apr 2016 13:40:01 +0900 (JST)
> From: Tino Calancha <f92capac@gmail.com>
> 
> Interactive calls to `insert-char' cannot find all
> characters when CHARACTER is the unicode character name.
> 
> IOW, it finds all characters when CHARACTER is the
> code point.
> 
> 
> emacs -Q:
> M-x insert-char RET cjk SPC TAB
> ;; Buffer "*Completions*" just shows entries starting
> ;; with 'CJK RADICAL' or 'CJK STROKE'.
> 
> M-x insert-char RET 2eea RET
> ;; ok
> M-x insert-char RET cjk SPC radical SPC c-simplified SPC frog RET
> ;; ok
> M-x insert-char RET 79c1 RET
> ;; ok
> M-x insert-char RET cjk SPC ideograph-79c1 RET
> ;; Signal error 'Invalid character'

It's a feature, see ucs-names.  We deliberately filter out
non-descriptive names like "CJK COMPATIBILITY IDEOGRAPH-2F803",
because (a) if we didn't the list of completions would be sometimes
much longer; and (b) it makes very little sense to show these names as
completions candidates, because those names include the codepoint, so
if you know which of these you need to insert, you can insert it by
the codepoint.