Replace many instances of read-file-name with read-directory-name.

Replace many instances of read-file-name with read-directory-name.

* lisp/files.el (delete-directory, copy-directory, list-directory): Use
read-directory-name.

* lisp/find-file.el (ff-find-the-other-file):
* lisp/net/ange-ftp.el (ange-ftp-make-directory):
* lisp/printing.el (pr-interactive-dir):
* lisp/progmodes/ada-prj.el (ada-prj-load-directory):
* lisp/progmodes/ebnf2ps.el (ebnf-print-directory)
(ebnf-spool-directory, ebnf-eps-directory)
(ebnf-syntax-directory):
* lisp/shell.el (shell):
* lisp/speedbar.el (speedbar-create-directory):
* lisp/vc/emerge.el (emerge-merge-directories):
* lisp/vc/vc-dir.el (vc-dir):
* lisp/vc/vc.el (vc-create-tag, vc-retrieve-tag): Likewise.

* lisp/gnus.el (gnus-interactive): Use read-directory-name.

* lisp/gnus-uu.el (gnus-uu-decode-uu-and-save)
(gnus-uu-decode-unshar-and-save, gnus-uu-decode-save)
(gnus-uu-decode-binhex, gnus-uu-decode-yenc)
(gnus-uu-decode-save-view, gnus-uu-decode-postscript-and-save):
Likewise.

* lisp/mh-funcs.el (mh-store-msg, mh-store-buffer):
* lisp/mh-mime.el (mh-mime-save-parts): Use read-directory-name.

* lisp/dired.el: Clarify comment.