* doc/lispref/display.texi (Size of Displayed Text): Document
'truncate-string-ellipsis'.
* lisp/international/mule-util.el (truncate-string-ellipsis): Doc fix.
(truncate-string-to-width): Mention in the doc string that the
default for ELLIPSIS comes from 'truncate-string-ellipsis'.
* etc/NEWS: Move the 'truncate-string-ellipsis' entry to the "Lisp
Changes" section.