bug#13084: boyer_moore crashes with certain characters in the case table

[Juri Linkov]

>> So the dataflow to get the canonical character will be Á -> A -> a.
>> If `case-fold-search' is nil, then Á -> A.  If a new variable
>> `decomposition-search' (or `normalized-search') is nil then Á -> á.
>
> Any such table should allow handling asymmetric searches: That is,
> searching for "ába" should match "ába" "ábà" and "ábá" but not "aba" or
> "àbá".  Can we do that?

IIUC what you mean is something like `search-upper-case'
where upper case chars disable case fold searching,
so "Aba" should match "Aba" and "AbA" but not "aba".