[development] Connecting to multiple databases in 5.x

Now that the settings.php file is write protected, the instructions at http://drupal.org/node/18429 no longer work to connect to multiple databases. I searched around but wasn't able to find anything on a recommended way to do this in 5.x. And, of course, the documentation on that page needs to be updated, too. I posted a comment on http://drupal.org/node/64279, but I'm not sure that was the best place to put it. Karen