I have questions about two variables losing global scope and whether we need to globalize them:
$mu_plugins, an array of PHP files from the must use plugins folder. We unset the corresponding array holding plain WP plugins to include. It is used nowhere in core and I highly doubt it needs to remain a global.
$prefix, as in $prefix = $wpdb->set_prefix($table_prefix); -- which is then checked for is_wp_error().
I think the answer to both is no (just being cautious), in which case 11881.5.diff is good on my end.