Assign the size of the screen to the root window
Assign the size of the screen to the root window

On startup, the root window got assigned the size of the main screen.
But, the GdkScreen has the width of all screens/monitors connected to the
machine.  Change this so that in _gdk_windowing_window_init, we assign
the width/height of all monitors to the root window width, height.
Should fix bug 594738.

Adamovskiy/gtk,grubersjoe/adwaita,msteinert/gtk,nacho/gtk-,davidt/gtk,Sidnioulz/SandboxGtk,johne53/MB3Gtk-2,ahodesuka/gtk,Unity-Technologies/gtk,johne53/MB3Gtk-2,ahodesuka/gtk,jadahl/gtk,jessevdk/gtk,ahodesuka/gtk,Lyude/gtk-,jadahl/gtk,Lyude/gtk-,grubersjoe/adwaita,ebassi/gtk,jigpu/gtk,davidt/gtk,jadahl/gtk,nacho/gtk-,jigpu/gtk,chergert/gtk,davidgumberg/gtk,alexlarsson/gtk,davidgumberg/gtk,davidt/gtk,bratsche/gtk-,Distrotech/gtk,Distrotech/gtk2,simokivimaki/gtk,jadahl/gtk,ebassi/gtk,alexlarsson/gtk,jigpu/gtk,Adamovskiy/gtk,Lyude/gtk-,bratsche/gtk-,nacho/gtk-,davidt/gtk,davidgumberg/gtk,Distrotech/gtk,alexlarsson/gtk,alexlarsson/gtk,Distrotech/gtk2,simokivimaki/gtk,jigpu/gtk,Adamovskiy/gtk,bratsche/gtk-,Adamovskiy/gtk,chipx86/gtk,jadahl/gtk,Unity-Technologies/gtk,jadahl/gtk,simokivimaki/gtk,Sidnioulz/SandboxGtk,bratsche/gtk-,davidt/gtk,Lyude/gtk-,Distrotech/gtk,grubersjoe/adwaita,Sidnioulz/SandboxGtk,Distrotech/gtk2,ahodesuka/gtk,jigpu/gtk,Lyude/gtk-,chipx86/gtk,johne53/MB3Gtk-2,Adamovskiy/gtk,jessevdk/gtk,jigpu/gtk,simokivimaki/gtk,jessevdk/gtk,davidgumberg/gtk,Sidnioulz/SandboxGtk,Unity-Technologies/gtk,chergert/gtk,grubersjoe/adwaita,grubersjoe/adwaita,bratsche/gtk-,davidgumberg/gtk,simokivimaki/gtk,simokivimaki/gtk,Adamovskiy/gtk,msteinert/gtk,jigpu/gtk,Lyude/gtk-,Adamovskiy/gtk,Sidnioulz/SandboxGtk,Lyude/gtk-,Distrotech/gtk2,jessevdk/gtk,grubersjoe/adwaita,davidgumberg/gtk,chergert/gtk,alexlarsson/gtk,johne53/MB3Gtk-2,davidt/gtk,ahodesuka/gtk,ebassi/gtk,alexlarsson/gtk,ebassi/gtk,grubersjoe/adwaita,ahodesuka/gtk,chipx86/gtk,Unity-Technologies/gtk,jessevdk/gtk,davidgumberg/gtk,msteinert/gtk,alexlarsson/gtk,ahodesuka/gtk,Adamovskiy/gtk,msteinert/gtk,ahodesuka/gtk,jessevdk/gtk,chergert/gtk,alexlarsson/gtk,nacho/gtk-,Distrotech/gtk2,jadahl/gtk,Sidnioulz/SandboxGtk,chergert/gtk,grubersjoe/adwaita,ebassi/gtk,Distrotech/gtk,chipx86/gtk,Lyude/gtk-,msteinert/gtk,jigpu/gtk,chergert/gtk,ebassi/gtk,Distrotech/gtk2,davidgumberg/gtk,jadahl/gtk,nacho/gtk-,msteinert/gtk,bratsche/gtk-,chipx86/gtk,chergert/gtk,Distrotech/gtk,Unity-Technologies/gtk,chergert/gtk,johne53/MB3Gtk-2,jessevdk/gtk