bug#28439: suggestion: support case-independent

[Winston]

>>     Sure, since I like it here, I might like it elsewhere, but I won't
>> know until those situations come up, and if I don't like it elsewhere,
>> then I'd be stuck.

> I'd like to know of one such example, if it happens.

OK, but if it's a couple years from now before it happens, I'm likely to
assume you're not still interested.  :)

>> * xref-completion-ignore-case, default t;

>> * creating something that applies to both completions and
>>    find-definition (I didn't save the patch, but my vague
>>    recollection is that it just defaulted to using t for
>>    completions).

> Not sure what this means, need details.

The first was a variable that only affects completions.

The second controls both completions and what xref-find-definitions
matches, so either both would allow case folding or both would not.
 -WBE