Among others, add a remapping for C-x 4 d, cf. Bug#26360.
* lisp/ido.el (ido-mode): Remap missing commands.
(ido-file-internal, ido-visit-buffer): Add support for new
methods.
(ido-display-buffer-other-frame)
(ido-find-alternate-file-other-window, ido-dired-other-window)
(ido-dired-other-frame): New commands.
* test/lisp/ido-tests.el (ido-tests--other-window-frame): Add unit
test for the bindings.
