add hint to turn of magic quotes

README.rst

@@ -28,6 +28,7 @@ Before you install the app check that the following requirements are met:
 
 - Your database uses utf-8
 - Your webserver uses utf-8
+- `Magic quotes are turned off <http://php.net/manual/de/security.magicquotes.disabling.php>`_
 - You use a browser that supports the FileReader API
 - You can use a cron or webcron to call Background Jobs in ownCloud
 - (optional) install php-curl