code: public Content getNavLinkNext() {
          Content nextletterLabel = getResource("doclet.Next_Letter");
          if (next == -1) {
              return HtmlTree.LI(nextletterLabel);
          }
          else {
              Content nextLink = getHyperLink(DocPaths.indexN(next),
                      nextletterLabel);
              return HtmlTree.LI(nextLink);
          }
      }
docs: Get link to the next unicode character.
  
  @return a content tree for the link