[2.0.1] Implement error collection for RemoveForeignElements.

- Register Generator context variable.
- Implement special substitutions for error collector.
- Also sort by order the errors came in.
- Fix line number determination bug in Lexer::create().
- Remove vestigial variables.
- Force all tag transforms to use copy(), implement serialize, unserialize algorithm for copy() in tokens.

git-svn-id: http://htmlpurifier.org/svnroot/htmlpurifier/trunk@1238 48356398-32a2-884e-a903-53898d9a118a

library/HTMLPurifier/Lexer.php

@@ -155,7 +155,11 @@ class HTMLPurifier_Lexer
             
             // once PHP DOM implements native line numbers, or we
             // hack out something using XSLT, remove this stipulation
-            if ($config->get('Core', 'MaintainLineNumbers')) {
+            $line_numbers = $config->get('Core', 'MaintainLineNumbers');
+            if (
+                $line_numbers === true ||
+                ($line_numbers === null && $config->get('Core', 'CollectErrors'))
+            ) {
                 $lexer = 'DirectLex';
                 break;
             }