[feature/auth-refactor] Provider Interface Skeleton

Creates a skeleton of the authentication provider interface.

PHPBB3-9734

phpBB/includes/auth/provider_interface.php

@@ -0,0 +1,32 @@
+<?
+/**
+*
+* @package auth
+* @copyright (c) 2013 phpBB Group
+* @license http://opensource.org/licenses/gpl-2.0.php GNU General Public License v2
+*
+*/
+
+/**
+* @ignore
+*/
+if (!defined('IN_PHPBB'))
+{
+	exit;
+}
+
+/**
+ * The interface authentication provider classes have to implement.
+ *
+ * @package auth
+ */
+class phpbb_auth_provider_interface
+{
+	public function init();
+
+	public function login();
+
+	public function autologin();
+
+	public function acp();
+}