OS.Path.fold may fold over initially provided dotfiles even though ~dotfiles is false

[dbuenzli]

The problem is that we simply Fpath.normalize the initially provided paths and consult its basename. Of course this won't work e.g. if the directory pointed by an initial path like ../../ is a dotfile (e.g. .emacs.d when you are inside it). The only way to solve the problem is replace the call to Fpath.normalize by a call to realpath(3) once #49 has been solved and check the last non-empty segment of the result doesn't start with a dot.