Revert "remove htmlpurifier"

This reverts commit c21a462d52.

lib/htmlpurifier/library/HTMLPurifier/HTMLModule/TargetBlank.php

@@ -0,0 +1,19 @@
+<?php
+
+/**
+ * Module adds the target=blank attribute transformation to a tags.  It
+ * is enabled by HTML.TargetBlank
+ */
+class HTMLPurifier_HTMLModule_TargetBlank extends HTMLPurifier_HTMLModule
+{
+
+    public $name = 'TargetBlank';
+
+    public function setup($config) {
+        $a = $this->addBlankElement('a');
+        $a->attr_transform_post[] = new HTMLPurifier_AttrTransform_TargetBlank();
+    }
+
+}
+
+// vim: et sw=4 sts=4