fixed config var `password_hash_algo` string to constant and added info link

application/config/aauth.php

@@ -68,7 +68,7 @@ defined('BASEPATH') OR exit('No direct script access allowed');
 |	['hash']							Name of selected hashing algorithm (e.g. "md5", "sha256", "haval160,4", etc..)
 |										Please, run hash_algos() for know your all supported algorithms
 | 	['use_password_hash']               True to use PHP's own password_hash() function with BCrypt, needs PHP5.5 or higher
-| 	['password_hash_algo']              password_hash algorithm ("PASSWORD_DEFAULT", "PASSWORD_BCRYPT") 
+| 	['password_hash_algo']              password_hash algorithm (PASSWORD_DEFAULT, PASSWORD_BCRYPT) for details see http://php.net/manual/de/password.constants.php
 | 	['password_hash_options']           password_hash options array for details see http://php.net/manual/en/function.password-hash.php
 |
 */
@@ -128,7 +128,7 @@ $config_aauth["default"] = array(
 
 	'hash'                           => 'sha256',
 	'use_password_hash'              => false,
-	'password_hash_algo'             => 'PASSWORD_DEFAULT',
+	'password_hash_algo'             => PASSWORD_DEFAULT,
 	'password_hash_options'          => array()
 );