(font-lock-keywords): Fix doc for multiline matches.

(font-lock-keywords): Fix doc for multiline matches.
(font-lock-add-keywords): Make it work even if font-lock-mode is nil,
so that it can be used more easily in <foo>-mode-hook.  Also make sure
to avoid duplicate entries.
(font-lock-update-removed-keyword-alist): Renamed `major-mode'->`mode'.
(font-lock-remove-keywords): Just as was done for `add', allow it to
work even if font-lock-mode is nil.  Also make sure we don't modify
any pre-existing list by forcing a copy-sequence.  Finally rename
`major-mode' to `mode'.
(font-lock-fontify-syntactic-anchored-keywords)
(font-lock-fontify-anchored-keywords)
(font-lock-fontify-keywords-region): Use line-end-position.
Don't make `font-lock-multiline' local (it's now done in
font-lock-set-defaults).
(font-lock-set-defaults): Make `font-lock-multiline' local.  Also
move the `font-lock-fontified' creation to inside the `unless'.