Silence ediff compilation

Silence ediff compilation

* lisp/vc/ediff-diff.el, lisp/vc/ediff-merg.el: Require ediff-util at run-time.

* lisp/vc/ediff-mult.el: Adjust requires.
(ediff-directories-internal, ediff-directory-revisions-internal)
(ediff-patch-file-internal): Declare.

* lisp/vc/ediff-ptch.el: Adjust requires.
(ediff-use-last-dir, ediff-buffers-internal): Declare.
(ediff-find-file): Autoload.

* lisp/vc/ediff-util.el: No need to load ediff when compiling.
(ediff-regions-internal): Declare.

* lisp/vc/ediff-wind.el: Adjust requires.
(ediff-compute-toolbar-width): Define when compiling.
(ediff-setup-control-buffer, ediff-make-bottom-toolbar): Declare.

* lisp/vc/ediff.el: No need to load dired, ediff-ptch when compiling.
(dired-get-filename, dired-get-marked-files)
(ediff-last-dir-patch, ediff-patch-default-directory)
(ediff-get-patch-buffer, ediff-dispatch-file-patching-job)
(ediff-patch-buffer-internal): Declare.