MDL-31785 import HTMLPurifier 4.4.0+

Includes one extra fix for _blank 8c9d461a6259d7b8ac4ae5c9c9e95ab176cfcda3 compared to 4.4.0 release.

lib/htmlpurifier/HTMLPurifier.php

@@ -19,7 +19,7 @@
  */
 
 /*
-    HTML Purifier 4.3.0 - Standards Compliant HTML Filtering
+    HTML Purifier 4.4.0 - Standards Compliant HTML Filtering
     Copyright (C) 2006-2008 Edward Z. Yang
 
     This library is free software; you can redistribute it and/or
@@ -55,10 +55,10 @@ class HTMLPurifier
 {
 
     /** Version of HTML Purifier */
-    public $version = '4.3.0';
+    public $version = '4.4.0';
 
     /** Constant with version of HTML Purifier */
-    const VERSION = '4.3.0';
+    const VERSION = '4.4.0';
 
     /** Global configuration object */
     public $config;