panels_node_update_6001 uses d6 version of db_add_field()

d7 version of db_add_field() is db_add_field($table, $field, $spec, $keys_new = array()) whereas panels_node_update_6001() uses it like db_add_field(&$ret, $table, $field, $spec, $new_keys = array()). This causes an error when updating from d6 to d7 via update.php:

The following updates returned messages
panels_node module
Update #6001

    * Failed: DatabaseSchemaObjectDoesNotExistException: Cannot add field .panels_node: table doesn't exist. in DatabaseSchema_mysql->addField() (line 321 of /var/www/drupalupgrade/includes/database/mysql/schema.inc).

Changing function to the following should fix:

/**
 * Implementation of hook_update to handle adding a pipeline
 */
function panels_node_update_6001() {
  $field = array(
    'type' => 'varchar',
    'length' => '255',
  );

  db_add_field('panels_node', 'pipeline', $field);
}