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/Injector/RemoveSpansWithoutAttributes.php

@@ -0,0 +1,60 @@
+<?php
+
+/**
+ * Injector that removes spans with no attributes
+ */
+class HTMLPurifier_Injector_RemoveSpansWithoutAttributes extends HTMLPurifier_Injector
+{
+    public $name = 'RemoveSpansWithoutAttributes';
+    public $needed = array('span');
+
+    private $attrValidator;
+
+    /**
+     * Used by AttrValidator
+     */
+    private $config;
+    private $context;
+
+    public function prepare($config, $context) {
+        $this->attrValidator = new HTMLPurifier_AttrValidator();
+        $this->config = $config;
+        $this->context = $context;
+        return parent::prepare($config, $context);
+    }
+
+    public function handleElement(&$token) {
+        if ($token->name !== 'span' || !$token instanceof HTMLPurifier_Token_Start) {
+            return;
+        }
+
+        // We need to validate the attributes now since this doesn't normally
+        // happen until after MakeWellFormed. If all the attributes are removed
+        // the span needs to be removed too.
+        $this->attrValidator->validateToken($token, $this->config, $this->context);
+        $token->armor['ValidateAttributes'] = true;
+
+        if (!empty($token->attr)) {
+            return;
+        }
+
+        $nesting = 0;
+        $spanContentTokens = array();
+        while ($this->forwardUntilEndToken($i, $current, $nesting)) {}
+
+        if ($current instanceof HTMLPurifier_Token_End && $current->name === 'span') {
+            // Mark closing span tag for deletion
+            $current->markForDeletion = true;
+            // Delete open span tag
+            $token = false;
+        }
+    }
+
+    public function handleEnd(&$token) {
+        if ($token->markForDeletion) {
+            $token = false;
+        }
+    }
+}
+
+// vim: et sw=4 sts=4