dired-dwim-target uses most recently visited window instead of next window.
* doc/emacs/dired.texi (Operating on Files): Document behavior change.
* lisp/dired-aux.el (dired-dwim-target-directories): New function.
(dired-dwim-target-directory, dired-dwim-target-defaults): Use it
to get the most recently used window instead of the next window (bug#35385).
* lisp/dired.el (dired-dwim-target): Doc fix.
* test/lisp/dired-tests.el: Remove unnecessary require and pacify
byte-compiler.