* lisp/vc/diff-mode.el (diff--revert-kill-hunks): New workhorse
routine.
(diff-hunk-kill, diff-revert-and-kill-hunk): Call it.
(diff-hunk-kill): New BEG and END parameters and interactive
form.
* doc/emacs/files.texi (Diff Mode):
* etc/NEWS: Document the change.