wp-db.php is now always included. Databa…

wp-db.php is now always included. Database drop-ins should continue to work without any adjustment in most cases (or can be adjusted to work with small tweaks).

This is for performance as we are no longer conditionally including a file. It also allows db.php files to cleanly extend wpdb, which previously required a bit of tinkering.

See https://core.trac.wordpress.org/ticket/14508.

#3-1, #dev-notes