comment-line-break-function is not buffer-local

[Juanma Barranquero]

Doc for comment-line-break-function says:

(defvar comment-line-break-function 'comment-indent-new-line
[...]
Setting this variable automatically makes it local to the current buffer.")

which is not true, and it seems it never was. (It was added at
http://savannah.gnu.org/cgi-bin/viewcvs/emacs/emacs/lisp/simple.el.diff?r1=1.317&r2=1.318),
with the comment but no `make-variable-buffer-local' or equivalent.

What's preferable? Fixing the doc, or adding
`make-variable-buffer-local'? (I'm partial to the first option.)

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                    /L/e/k/t/u