code: boolean isBuiltin(Class clazz) {
          return clazz == null ? false
                               : builtin.contains(clazz.getName());
      }
docs: Retrieves whether the indicated Class object is systematically
  granted to PUBLIC in support of core operation. <p>
  
  @return whether the indicated Class object is systematically
  granted to PUBLIC in support of core operation
  @param clazz The Class object for which to make the determination