GitLab

Add separator.pbm tool-bar image

* etc/images/separator.pbm: New file.  Having it avoids the side
effect of changing the tool-bar height when the default font's size
changes and XPM image support is not available, due to the SPC
characters that are left in the Lisp string used to display the tool
bar, because there are no images to display instead of those SPC
characters.