(log-edit-maximum-comment-ring-size, log-edit-comment-ring)

(log-edit-maximum-comment-ring-size, log-edit-comment-ring)
(log-edit-comment-ring-index, log-edit-last-comment-match): Rename vars from
vc-maximum-comment-ring-size, vc-comment-ring, vc-comment-ring-index,
and vc-last-comment-match.
(log-edit-new-comment-index, log-edit-previous-comment)
(log-edit-next-comment, log-edit-comment-search-backward)
(log-edit-comment-search-forward, log-edit-comment-to-change-log):
Rename funs from vc-new-comment-index, vc-previous-comment,
vc-next-comment, vc-comment-search-reverse, vc-comment-search-forward,
and vc-comment-to-change-log.