(comment-string-strip): Strip terminating newlines.

(comment-string-strip): Strip terminating newlines.
(comment-search-forward): Make LIMIT compulsory.
  If an unterminated string (rather than a comment) is found, try again,
  assuming that the region starts inside a string.
(comment-beginning): Make sure we don't move if we find a comment but
  it's not the one we're in.
(comment-enter-backward): Handle the case where comment-end-skip fails.
(comment-indent): Normalize variables and use line-end-position.
(comment-kill): Use line-end-position.
(comment-spill): Remove.
(comment-indent-new-line): Renamed from indent-new-comment-line.
  Cleaned up old commented-out code.
  Reset comment-continue and comment-end before calling comment-indent.