Cycles: refactor kernel closure storage to use structs per closure type.

Reviewed By: dingto, sergey

Differential Revision: https://developer.blender.org/D2127

intern/cycles/render/graph.cpp

@@ -967,6 +967,9 @@ int ShaderGraph::get_num_closures()
 		else if(CLOSURE_IS_GLASS(closure_type)) {
 			num_closures += 2;
 		}
+		else if(CLOSURE_IS_BSDF_MULTISCATTER(closure_type)) {
+			num_closures += 2;
+		}
 		else {
 			++num_closures;
 		}