Enable Case sensitive when specifying an upper case letter

[arialdomartini]

I have a suggestion: make search case sensitive if the user specifies an upper case letter.

I believe this is consistent with how Emacs manages searching and case:

An upper-case letter anywhere in the incremental search string makes the search case-sensitive.

Of course, this should happen only in case ace-jump is set to be case insensitive (e.g. (setq ace-jump-mode-case-fold nil)); with (setq ace-jump-mode-case-fold t) then the letter should match exactly, including case.