(do-auto-fill): Fill, don't fill, or fill-and-justify

(do-auto-fill): Fill, don't fill, or fill-and-justify
depending on setting of justification text-property.  Respect
left-margin and right-margin text properties.
(open-line, indent-new-comment-line): Inherit when inserting.
(newline-and-indent, reindent-then-newline-and-indent): Doc fix.