bug#25169: 26.0.50; display-buffer doesn't set window width correctly

[Liu Hui]

Recipe 1:

1. Emacs -Q
2. evaluate the following code in *scratch*:

   (display-buffer (get-buffer-create "aaa")
                  '(display-buffer-pop-up-window
                    (window-width . 20)))
   ;; => correct window width for buffer "aaa"

   (display-buffer (get-buffer-create "bbb")
                  '(display-buffer-pop-up-window
                    (window-width . 20)))
   ;; => changed and larger window width for buffer "bbb"


Recipe 2:

1. Emacs -Q
2. evaluate the following code in *scratch*:

   (display-buffer (get-buffer-create "aaa")
                  '(display-buffer-in-side-window
                    (window-width . 20)
                    (side . right)))
   ;; => correct window width for buffer "aaa"

   (display-buffer (get-buffer-create "bbb")
                  '(display-buffer-in-side-window
                    (window-width . 20)
                    (side . left)))
   ;; => correct width for buffer "bbb", but the window width of
   ;; buffer "aaa" is changed and becomes larger


In GNU Emacs 26.0.50.2 (x86_64-pc-linux-gnu, GTK+ Version 3.18.9)
 of 2016-12-10 built on lgw01-57
Windowing system distributor 'The X.Org Foundation', version 11.0.11804000
System Description:     Ubuntu 16.04.1 LTS