Checkdoc fixes in `vc/*.el`

Checkdoc fixes in `vc/*.el`

* lisp/vc/ediff-init.el (ediff-start-narrowed)
(ediff-buffer-values-orig-A, ediff-buffer-values-orig-B)
(ediff-buffer-values-orig-C, ediff-buffer-values-orig-Ancestor):
* lisp/vc/ediff-mult.el:
* lisp/vc/ediff-ptch.el (ediff-get-patch-buffer):
* lisp/vc/emerge.el (emerge-before-flag, emerge-after-flag):
* lisp/vc/vc-dav.el (vc-dav-checkin):
* lisp/vc/vc-git.el (vc-git-command):
* lisp/vc/vc-hg.el (vc-hg-command):
* lisp/vc/vc-src.el (vc-src-command):
* lisp/vc/vc-svn.el (vc-svn-command):
* lisp/vc/vc.el (vc-checkin): Checkdoc fixes.