* vc.el (vc-trunk-p): Rename to vc-rcs-trunk-p and move to vc-rcs.el.

* vc.el (vc-trunk-p): Rename to vc-rcs-trunk-p and move to vc-rcs.el.
(vc-minor-part): Rename to vc-rcs-minor-part and move to vc-rcs.el.
(vc-default-previous-revision): Rename to vc-rcs-previous-revision
and move to vc-rcs.el.
(vc-default-next-revision): Rename to vc-rcs-next-revision and
move to vc-rcs.el.
(vc-cvs-update-changelog): Move to vc-cvs.el, use vc-call-backend.
(vc-rcs-update-changelog): Remove.
(vc-update-changelog-rcs2log): Rename to vc-rcs-update-changelog
and move to vc-rcs.el.

* vc-rcs.el (vc-rcs-latest-on-branch-p, vc-rcs-checkin)
(vc-rcs-checkout, vc-rcs-rollback): Adjust for the vc-rcs-trunk-p
renaming.
(vc-rcs-trunk-p, vc-rcs-minor-part, vc-rcs-previous-revision)
(vc-rcs-next-revision, vc-rcs-update-changelog): Moved here from
vc.el, renamed to be RCS specific.

* vc-cvs.el (vc-cvs-previous-revision, vc-cvs-next-revision): New functions.
(vc-cvs-update-changelog): Moved here from vc.el.

* vc-sccs.el (vc-sccs-previous-revision, vc-sccs-next-revision):
New functions.