Add website to client repository

Closes #1567

The main reason I'm not simply merging Annika's PR is because this
way makes it clearer that I'm taking responsibility for all this
code, that it's mostly code I wrote, and also because it makes it
easier to ensure that none of the files have been changed.

(Not that I don't personally trust Annika, but I have something
resembling an obligation to users not to expose them to risks based
on personal trust.)

website/lib/htmlpurifier/HTMLPurifier/Strategy/ValidateAttributes.php

@@ -0,0 +1,39 @@
+<?php
+
+/**
+ * Validate all attributes in the tokens.
+ */
+
+class HTMLPurifier_Strategy_ValidateAttributes extends HTMLPurifier_Strategy
+{
+
+    public function execute($tokens, $config, $context) {
+
+        // setup validator
+        $validator = new HTMLPurifier_AttrValidator();
+
+        $token = false;
+        $context->register('CurrentToken', $token);
+
+        foreach ($tokens as $key => $token) {
+
+            // only process tokens that have attributes,
+            //   namely start and empty tags
+            if (!$token instanceof HTMLPurifier_Token_Start && !$token instanceof HTMLPurifier_Token_Empty) continue;
+
+            // skip tokens that are armored
+            if (!empty($token->armor['ValidateAttributes'])) continue;
+
+            // note that we have no facilities here for removing tokens
+            $validator->validateToken($token, $config, $context);
+
+            $tokens[$key] = $token; // for PHP 4
+        }
+        $context->destroy('CurrentToken');
+
+        return $tokens;
+    }
+
+}
+
+// vim: et sw=4 sts=4