I refactored the new authenticator code. Now you can easily enable/disable the various authentication methods in sapphire/_config.php.
Because we have now that new configuration file, the code that changed PHPs include path isn't needed anymore in your mysite/_config.php, so simple delete it (and the constant definition) there.
The only thing where you may have to add it is the installer when you do a clean install, but since it isn't under version control I can't add the code there.
I wish you all a great weekend,