book.module needs ORDER BY columns in SELECT portion of queries

Hi,

I'm running Drupal on PostgreSQL 8.0.1 and had to modify the book module a little bit to make it work on my system. It's pretty minor--you just have to ensure that you are also SELECTing all the columns you're using in your ORDER BY expression, otherwise PostgreSQL will reject the query.

These changes should have zero ramifications for MySQL installations.

Here is a patch against 4.6.2 which makes these changes.