Made the rest of the db classes abstract \n
except for the DB_cache class, because I'm not sure if it is directly called
diff --git a/system/database/DB_forge.php b/system/database/DB_forge.php
index fe2a677..192b78f 100644
--- a/system/database/DB_forge.php
+++ b/system/database/DB_forge.php
@@ -34,7 +34,7 @@
  * @author		EllisLab Dev Team
  * @link		http://codeigniter.com/user_guide/database/
  */
-class CI_DB_forge {
+abstract class CI_DB_forge {
 
 	public $fields		= array();
 	public $keys		= array();
diff --git a/system/database/DB_result.php b/system/database/DB_result.php
index c3cdd24..d0205e0 100644
--- a/system/database/DB_result.php
+++ b/system/database/DB_result.php
@@ -36,7 +36,7 @@
  * @author		EllisLab Dev Team
  * @link		http://codeigniter.com/user_guide/database/
  */
-class CI_DB_result {
+abstract class CI_DB_result {
 
 	public $conn_id				= NULL;
 	public $result_id			= NULL;
diff --git a/system/database/DB_utility.php b/system/database/DB_utility.php
index c94f93e..a7db803 100644
--- a/system/database/DB_utility.php
+++ b/system/database/DB_utility.php
@@ -32,7 +32,7 @@
  * @author		EllisLab Dev Team
  * @link		http://codeigniter.com/user_guide/database/
  */
-class CI_DB_utility extends CI_DB_forge {
+abstract class CI_DB_utility extends CI_DB_forge {
 
 	public $db;
 	public $data_cache		= array();