/**
 * Execute WordPress role creation for the various WordPress versions.
 *
 * @since 2.0.0
 */
function populate_roles()
{
    populate_roles_160();
    populate_roles_210();
    populate_roles_230();
    populate_roles_250();
    populate_roles_260();
    populate_roles_270();
    populate_roles_280();
    populate_roles_300();
}

/**
 * Execute changes made in WordPress 2.7.
 *
 * @since 2.7.0
 */
function upgrade_270()
{
    global $wpdb, $wp_current_db_version;
    if ($wp_current_db_version < 8980) {
        populate_roles_270();
    }
    // Update post_date for unpublished posts with empty timestamp
    if ($wp_current_db_version < 8921) {
        $wpdb->query("UPDATE {$wpdb->posts} SET post_date = post_modified WHERE post_date = '0000-00-00 00:00:00'");
    }
}