New feature: Splitting an object into a multi-part volume.

xs/xsp/Model.xsp

@@ -297,6 +297,8 @@ ModelMaterial::attributes()
         %code%{ RETVAL = THIS->modifier; %};
     void set_modifier(bool modifier)
         %code%{ THIS->modifier = modifier; %};
+
+    size_t split();
     
     ModelMaterial* assign_unique_material();
 };