Cycles: Initial support for volume ray visibility.

This adds a new "Volume Scatter" option to the "Ray Visibility" panels and can be used to e.g. exclude lamps from having an influence on the volume. See release logs for an example: http://wiki.blender.org/index.php/Dev:Ref/Release_Notes/2.72/Cycles

Differential revision: https://developer.blender.org/D771

intern/cycles/blender/addon/properties.py

@@ -731,6 +731,11 @@ class CyclesVisibilitySettings(bpy.types.PropertyGroup):
                 description="Object visibility for shadow rays",
                 default=True,
                 )
+        cls.scatter = BoolProperty(
+                name="Volume Scatter",
+                description="Object visibility for volume scatter rays",
+                default=True,
+                )
 
     @classmethod
     def unregister(cls):