bug#54804: 29.0.50; zap-to-char: case sensitive for upper-case letter

[Juri Linkov]

> This is what Emacs does for isearch/search.
>
> If you go to the *scratch* buffer, and you do
> C-s T C-s C-s
> you only jump on 'T', that is, you skip the 't'. This is regardless
> on the `case-fold-search' value.

Isearch has an additional option 'search-upper-case', although
I'm not sure if such complexity is worthy to add to zap-to.
Maybe only for interactive use.