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/PropertyListIterator.php

@@ -0,0 +1,32 @@
+<?php
+
+/**
+ * Property list iterator. Do not instantiate this class directly.
+ */
+class HTMLPurifier_PropertyListIterator extends FilterIterator
+{
+
+    protected $l;
+    protected $filter;
+
+    /**
+     * @param $data Array of data to iterate over
+     * @param $filter Optional prefix to only allow values of
+     */
+    public function __construct(Iterator $iterator, $filter = null) {
+        parent::__construct($iterator);
+        $this->l = strlen($filter);
+        $this->filter = $filter;
+    }
+
+    public function accept() {
+        $key = $this->getInnerIterator()->key();
+        if( strncmp($key, $this->filter, $this->l) !== 0 ) {
+            return false;
+        }
+        return true;
+    }
+
+}
+
+// vim: et sw=4 sts=4