The ability to create a window which will act, for some clients, as
the root window was first ventured into during the development of
Release 3.  Jim Fulton implemented a simple hack in Xlib which
simply replaced the 'root' member in each Screen structure with
the value found in a property placed on the real root window of the
screen.  The display name was augmented by appending the name of
this property; thus the application could be directed to the pseudo root
by specifying a different format for the display name.  Xlib would
parse this property name
