[3.0.0] Convert all $context calls away from references

- Update TODO list
- URISchemeRegistry doesn't return a reference for instance anymore, should do the same for other singletons

git-svn-id: http://htmlpurifier.org/svnroot/htmlpurifier/trunk@1477 48356398-32a2-884e-a903-53898d9a118a

library/HTMLPurifier/Generator.php

@@ -78,7 +78,7 @@ class HTMLPurifier_Generator
      * @param $config HTMLPurifier_Config object
      * @return Generated HTML
      */
-    public function generateFromTokens($tokens, $config, &$context) {
+    public function generateFromTokens($tokens, $config, $context) {
         $html = '';
         if (!$config) $config = HTMLPurifier_Config::createDefault();
         $this->_scriptFix   = $config->get('Output', 'CommentScriptContents');