Allow display inside display configuration

Submitted by Yan Pas

Assigned to Jérôme Guelfucci

Link to original bug (#12424)

Description

Sometimes it is unable to set equal resolutions on two displays, so the solution would be placing one display inside another one. Nvidia X server settings allows it, but xfce4-display settigs doesn't place one display inside another by drag and drop unfortunately.

Version: 4.12.0