Carlos Garnacho authored May 07, 2019 and Jonas Ådahl committed May 24, 2019

This object takes care of the X11 representation of the window stack,
namely the _NET_CLIENT_LIST and _NET_CLIENT_LIST_STACKING root window
properties.

This code has been lifted from src/core/stack.c into src/x11 as it's
dependent on the X11 display availability. This also leaves MetaStack
squeaky clean of x11 specifics.

!420