code: private boolean includeSuperclass(TypeElement superclass) {
          if (env.isIncluded(superclass)) return true;
          // TODO Make configurable:
          // See https://github.com/talsma-ict/umldoclet/issues/148
          return superclass.getModifiers().contains(Modifier.PUBLIC)
                  || superclass.getModifiers().contains(Modifier.PROTECTED);
      }
docs: Determine whether a superclass is included in the documentation.
  
  <p>
  Introduced to fix <a href="https://github.com/talsma-ict/umldoclet/issues/146">issue 146</a>:
  skip superclass if not included in the documentation.
  
  @param superclass The superclass to test.
  @return {@code true} if the superclass is within the documented javadoc part,
  or if its modifiers have the 'right' accesibility. See {#148} for accessibility details.