* lib/rdoc: Update to RDoc 4.1.0.preview.1

RDoc 4.1.0 contains a number of enhancements including a new default
  style and accessibility support.  You can see the changelog here:

  https://github.com/rdoc/rdoc/blob/v4.1.0.preview.1/History.rdoc

* test/rdoc:  ditto.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@42971 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/rdoc/markup/heading.rb

@@ -47,6 +47,19 @@ RDoc::Markup::Heading =
     "label-#{self.class.to_label.convert text.dup}"
   end
 
+  ##
+  # Creates a fully-qualified label which will include the label from
+  # +context+.  This helps keep ids unique in HTML.
+
+  def label context = nil
+    label = aref
+
+    label = [context.aref, label].compact.join '-' if
+      context and context.respond_to? :aref
+
+    label
+  end
+
   ##
   # HTML markup of the text of this label without the surrounding header
   # element.