Magento: add layout xml via event to add the layout file direct before local.xml

config.xml

<?xml version="1.0"?>
<config>
    <modules>
        <Loewenstark_Layout>
            <version>1.0.0.0</version>
        </Loewenstark_Layout>
    </modules>
    <global>
        <models>
            <loewenstark_layout>
                <class>Loewenstark_Layout_Model</class>
            </loewenstark_layout>
        </models>
        <events>
            <core_layout_update_updates_get_after>
                <observers>
                    <loewenstark_layout_add_layout_xml>
                        <type>singleton</type>
                        <class>loewenstark_layout/observer</class>
                        <method>addLayoutXml</method>
                    </loewenstark_layout_add_layout_xml>
                </observers>
            </core_layout_update_updates_get_after>     
        </events>
    </global>
</config>

Observer.php

<?php
class Loewenstark_Layout_Model_Observer
{

    // set loewenstark_layout.xml before local.xml
    public function addLayoutXml($event)
    {
        $xml = $event->getUpdates()
                ->addChild('loewenstark_layout');
        /* @var $xml SimpleXMLElement */
        $xml->addAttribute('module', 'Loewenstark_Layout');
        $xml->addChild('file', 'loewenstark_layout.xml');
    }
}