Replace existing autoloader with Composer-supplied

- Move Friendica namespace to `src`
- Move required `ezyang/htmlpurifier` to vendor
- Remove existing static autoloader
- Change boot.php reference to the autoloader

vendor/ezyang/htmlpurifier/library/HTMLPurifier/StringHash.php

@@ -0,0 +1,47 @@
+<?php
+
+/**
+ * This is in almost every respect equivalent to an array except
+ * that it keeps track of which keys were accessed.
+ *
+ * @warning For the sake of backwards compatibility with early versions
+ *     of PHP 5, you must not use the $hash[$key] syntax; if you do
+ *     our version of offsetGet is never called.
+ */
+class HTMLPurifier_StringHash extends ArrayObject
+{
+    /**
+     * @type array
+     */
+    protected $accessed = array();
+
+    /**
+     * Retrieves a value, and logs the access.
+     * @param mixed $index
+     * @return mixed
+     */
+    public function offsetGet($index)
+    {
+        $this->accessed[$index] = true;
+        return parent::offsetGet($index);
+    }
+
+    /**
+     * Returns a lookup array of all array indexes that have been accessed.
+     * @return array in form array($index => true).
+     */
+    public function getAccessed()
+    {
+        return $this->accessed;
+    }
+
+    /**
+     * Resets the access array.
+     */
+    public function resetAccessed()
+    {
+        $this->accessed = array();
+    }
+}
+
+// vim: et sw=4 sts=4