Use default-indent-new-line' instead of indent-new-comment-line'

* lisp/simple.el (default-indent-new-line): Doc string fix.

* lisp/textmodes/refill.el (refill-post-command-function): Make
default-indent-new-line work as indent-new-comment-line.

* lisp/textmodes/refill.el (refill-post-command-function): Bind
`M-C-j' and `M-j' to default-indent-new-line instead of
indent-new-comment-line to allow overriding via
`comment-line-break-function' (bug#12413).

lisp/bindings.el

@@ -1229,8 +1229,8 @@ if `inhibit-field-text-motion' is non-nil."
 (define-key ctl-x-map "\C-t" 'transpose-lines)
 
 (define-key esc-map ";" 'comment-dwim)
-(define-key esc-map "j" 'indent-new-comment-line)
-(define-key esc-map "\C-j" 'indent-new-comment-line)
+(define-key esc-map "j" 'default-indent-new-line)
+(define-key esc-map "\C-j" 'default-indent-new-line)
 (define-key ctl-x-map ";" 'comment-set-column)
 (define-key ctl-x-map [?\C-\;] 'comment-line)
 (define-key ctl-x-map "f" 'set-fill-column)

lisp/simple.el

@@ -7318,7 +7318,7 @@ indicating whether it should use soft newlines.")
 
 (defun default-indent-new-line (&optional soft)
   "Break line at point and indent.
-If a comment syntax is defined, call `comment-indent-new-line'.
+If a comment syntax is defined, call `comment-line-break-function'.
 
 The inserted newline is marked hard if variable `use-hard-newlines' is true,
 unless optional argument SOFT is non-nil."

lisp/textmodes/refill.el

@@ -181,7 +181,7 @@ complex processing.")
 	 (setq refill-doit nil)))
       ((or 'quoted-insert 'fill-paragraph 'fill-region) nil)
       ((or 'newline 'newline-and-indent 'open-line 'indent-new-comment-line
-           'reindent-then-newline-and-indent)
+           'default-indent-new-line 'reindent-then-newline-and-indent)
        ;; Don't zap what was just inserted.
        (save-excursion
 	 (beginning-of-line)		; for newline-and-indent