Upgrading to mediawiki 1.18

When I was upgrading my wikis to version 1.18, I encountered several problems. I resolved those problems, and to help users who run into the same issues I will document the solution here.

First problem: after upgrading, the URL http://<site>/mw-config/index.php does not work

When you, as per instruction in the UPGRADE readme file, browse to the URL http://<site>/mw-config/index.php, it does not show up.

If you look into the apache error log, you will find entries like

PHP Fatal error:  Cannot redeclare wfprofilein() (previously declared in /srv/www/htdocs/wiki/includes/profiler/Profiler.php:14) in /srv/www/htdocs/wiki/includes/ProfilerStub.php on line 24

This can be fixed by editing the file 'StartProfiler.php' in your wiki root.

Second problem: If you have FCKeditor, you get PHP Fatal error: Call to undefined method Parser::strip() in /srv/www/htdocs/wiki/extensions/FCKeditor/FCKeditor.body.php

For some reason, this new wiki does not like the installed FCKeditor. So I commented the line in LocalSettings.php:

// Use the FCK editor
#require_once("$IP/extensions/FCKeditor/FCKeditor.php");