bug#13177: 24.3.50; doc of `read-char-by-name'

[Juri Linkov]

>>> Dunno just what the intention was for this function.  If it really
>>> was to return a recognized Unicode character then this is a product
>>> bug and reading should not end until the user enters matching input
>>> (or hits `C-g').
>> As its docstring says, it also accepts a hexadecimal number
>> of Unicode code whose input can't use completion.
>
> That does not preclude using require-match.

I guess you mean adding a predicate that will check input
for a valid hex number?  It could act as an union of
character name completions and a predicate to check hex numbers.
But I don't imagine how to combine them without adding
a large list of all possible hex numbers to the completion list.