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/AttrDef/URI/IPv4.php

@@ -0,0 +1,45 @@
+<?php
+
+/**
+ * Validates an IPv4 address
+ * @author Feyd @ forums.devnetwork.net (public domain)
+ */
+class HTMLPurifier_AttrDef_URI_IPv4 extends HTMLPurifier_AttrDef
+{
+
+    /**
+     * IPv4 regex, protected so that IPv6 can reuse it.
+     * @type string
+     */
+    protected $ip4;
+
+    /**
+     * @param string $aIP
+     * @param HTMLPurifier_Config $config
+     * @param HTMLPurifier_Context $context
+     * @return bool|string
+     */
+    public function validate($aIP, $config, $context)
+    {
+        if (!$this->ip4) {
+            $this->_loadRegex();
+        }
+
+        if (preg_match('#^' . $this->ip4 . '$#s', $aIP)) {
+            return $aIP;
+        }
+        return false;
+    }
+
+    /**
+     * Lazy load function to prevent regex from being stuffed in
+     * cache.
+     */
+    protected function _loadRegex()
+    {
+        $oct = '(?:25[0-5]|2[0-4][0-9]|1[0-9]{2}|[1-9][0-9]|[0-9])'; // 0-255
+        $this->ip4 = "(?:{$oct}\\.{$oct}\\.{$oct}\\.{$oct})";
+    }
+}
+
+// vim: et sw=4 sts=4