Add conversion functions for our own tree format.

Signed-off-by: Edward Z. Yang <ezyang@mit.edu>

library/HTMLPurifier/Token/Empty.php

@@ -5,6 +5,11 @@
  */
 class HTMLPurifier_Token_Empty extends HTMLPurifier_Token_Tag
 {
+    public function toNode() {
+        $n = parent::toNode();
+        $n->empty = true;
+        return $n;
+    }
 }
 
 // vim: et sw=4 sts=4