* lisp/emacs-lisp/shadow.el (load-path-shadows-find): Check for
shadowing with case-insensitive matching for files of case-insensitive
directories (as determined by `file-name-case-insensitive-p').
* test/lisp/emacs-lisp/shadow-tests.el: New test.
* test/lisp/emacs-lisp/shadow-resources/p1/foo.el:
* test/lisp/emacs-lisp/shadow-resources/p2/FOO.el: New test files.