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/VarParser/Native.php

@@ -0,0 +1,26 @@
+<?php
+
+/**
+ * This variable parser uses PHP's internal code engine. Because it does
+ * this, it can represent all inputs; however, it is dangerous and cannot
+ * be used by users.
+ */
+class HTMLPurifier_VarParser_Native extends HTMLPurifier_VarParser
+{
+
+    protected function parseImplementation($var, $type, $allow_null) {
+        return $this->evalExpression($var);
+    }
+
+    protected function evalExpression($expr) {
+        $var = null;
+        $result = eval("\$var = $expr;");
+        if ($result === false) {
+            throw new HTMLPurifier_VarParserException("Fatal error in evaluated code");
+        }
+        return $var;
+    }
+
+}
+
+// vim: et sw=4 sts=4