[3.1.0] More PHP4->PHP5 conversions, notably reference removal of most methods that return objects

- Removed HTMLPurifier_Error
- Documentation updates
- Removed more copy() methods in favor of clone
- HTMLPurifier::getInstance() to HTMLPurifier::instance()
- Fix InterchangeBuilder to use HTMLPURIFIER_PREFIX

git-svn-id: http://htmlpurifier.org/svnroot/htmlpurifier/trunk@1689 48356398-32a2-884e-a903-53898d9a118a

library/HTMLPurifier/HTMLModule/Hypertext.php

@@ -9,7 +9,7 @@ class HTMLPurifier_HTMLModule_Hypertext extends HTMLPurifier_HTMLModule
     public $name = 'Hypertext';
     
     public function __construct() {
-        $a =& $this->addElement(
+        $a = $this->addElement(
             'a', 'Inline', 'Inline', 'Common',
             array(
                 // 'accesskey' => 'Character',