bug#19442: 25.0.50; Overflowing newline into right fringe requires left fringe to be nonempty

[Kirill Ignatiev]

According to overflow-newline-into-fringe's docstring, when point is
that the end of a line that is as wide as the frame the point should
be displayed in the right fringe.

However, it seems that on 25.0.50 (with -Q), it requires both the
right *and* the left fringe to be non-empty. If the left fringe is
empty, the newline does not overflow into the right fringe, as the
documentation and common sense says it should.

(setq overflow-newline-into-fringe t)
(dolist (x '((cursor-type . box)
             (cursor-color . "red")
             (width . 80)
             (left-fringe . 8) ; change this to 0
             (right-fringe . 8)))
  (set-frame-parameter (selected-frame) (car x) (cdr x)))
;; (progn (insert "\n;") (dotimes (x 79) (insert ?x)))
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In GNU Emacs 25.0.50.36 (x86_64-apple-darwin13.4.0, NS appkit-1265.21
Version 10.9.5 (Build 13F34))