; Fix documentation of package-vc.el

; Fix documentation of package-vc.el

* lisp/emacs-lisp/package-vc.el (package-vc-default-backend)
(package-vc-selected-packages, package-vc--archive-spec-alist)
(package-vc--archive-data-alist, package-vc--query-spec)
(package-vc--read-archive-data, package-vc-commit)
(package-vc--main-file, package-vc--generate-description-file)
(package-vc--build-documentation, package-vc--unpack-1)
(package-vc--guess-backend, package-vc--clone)
(package-vc--unpack, package-vc-update, package-vc--release-rev)
(package-vc-install, package-vc-checkout)
(package-vc-link-directory, package-vc-refresh)
(package-vc-prepare-patch, package-vc--archives-initialize): Doc fixes.