Update db.php

add multiple selects ids - like :
$db->select('table',  array('ID' => 'in (1,2,3,4)'), 10, false,'OR');
add print query mode (default false):
$db->select('table',  array(), limit, order,where_mode,print_query);
Merge pull request #1 from craiem/patch-1

Update db.php