New commands to create an empty file

New commands to create an empty file

Similarly as `create-directory', `dired-create-directory',
the new commands create the parent dirs as needed (Bug#24150).
* lisp/files.el (make-empty-file): New command.

* lisp/dired-aux.el (dired-create-empty-file): New command.
(dired--find-topmost-parent-dir): New function extracted
from `dired-create-directory'.
(dired-create-directory, dired-create-empty-file): Use it.

* lisp/dired.el (dired-mode-map):
Add menu entry for `dired-create-empty-file'.

* doc/emacs/dired.texi (Misc Dired Features)
* doc/lispref/files.texi (Create/Delete Dirs): Update manual.
; * etc/NEWS: Announce the changes.