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/IDAccumulator.php

@@ -0,0 +1,57 @@
+<?php
+
+/**
+ * Component of HTMLPurifier_AttrContext that accumulates IDs to prevent dupes
+ * @note In Slashdot-speak, dupe means duplicate.
+ * @note The default constructor does not accept $config or $context objects:
+ *       use must use the static build() factory method to perform initialization.
+ */
+class HTMLPurifier_IDAccumulator
+{
+
+    /**
+     * Lookup table of IDs we've accumulated.
+     * @public
+     */
+    public $ids = array();
+
+    /**
+     * Builds an IDAccumulator, also initializing the default blacklist
+     * @param HTMLPurifier_Config $config Instance of HTMLPurifier_Config
+     * @param HTMLPurifier_Context $context Instance of HTMLPurifier_Context
+     * @return HTMLPurifier_IDAccumulator Fully initialized HTMLPurifier_IDAccumulator
+     */
+    public static function build($config, $context)
+    {
+        $id_accumulator = new HTMLPurifier_IDAccumulator();
+        $id_accumulator->load($config->get('Attr.IDBlacklist'));
+        return $id_accumulator;
+    }
+
+    /**
+     * Add an ID to the lookup table.
+     * @param string $id ID to be added.
+     * @return bool status, true if success, false if there's a dupe
+     */
+    public function add($id)
+    {
+        if (isset($this->ids[$id])) {
+            return false;
+        }
+        return $this->ids[$id] = true;
+    }
+
+    /**
+     * Load a list of IDs into the lookup table
+     * @param $array_of_ids Array of IDs to load
+     * @note This function doesn't care about duplicates
+     */
+    public function load($array_of_ids)
+    {
+        foreach ($array_of_ids as $id) {
+            $this->ids[$id] = true;
+        }
+    }
+}
+
+// vim: et sw=4 sts=4