RhinoCycles: Changing wallpaper image doesn't show in Raytraced viewport.
RhinoCycles: Changing wallpaper image doesn't show in Raytraced viewport.

Add some memory to the background handling code so it can
figure out when the wallpaper image has been changed.

#RH-32415 Needs Testing
#RH-32415 Assigned to: marika.almgren

mcneel/RhinoCycles