Revert "Changed all db constructors to newer syntax, made insert_id() function more convenient for postgres on pdo driver"

This reverts commit f7a8d86dbc6805a4e52964bbea76738df75b5f35.
diff --git a/system/database/DB_cache.php b/system/database/DB_cache.php
index ad1c28d..3bf065c 100644
--- a/system/database/DB_cache.php
+++ b/system/database/DB_cache.php
@@ -33,7 +33,7 @@
 	 * Grabs the CI super object instance so we can access it.
 	 *
 	 */
-	function __construct(&$db)
+	function CI_DB_Cache(&$db)
 	{
 		// Assign the main CI object to $this->CI
 		// and load the file helper since we use it a lot
diff --git a/system/database/DB_driver.php b/system/database/DB_driver.php
index d7b63b9..237a4fc 100644
--- a/system/database/DB_driver.php
+++ b/system/database/DB_driver.php
@@ -78,7 +78,7 @@
 	 *
 	 * @param array
 	 */
-	function __construct($params)
+	function CI_DB_driver($params)
 	{
 		if (is_array($params))
 		{
diff --git a/system/database/DB_forge.php b/system/database/DB_forge.php
index 6bc4041..0dd29c2 100644
--- a/system/database/DB_forge.php
+++ b/system/database/DB_forge.php
@@ -35,7 +35,7 @@
 	 * Grabs the CI super object instance so we can access it.
 	 *
 	 */
-	function __construct()
+	function CI_DB_forge()
 	{
 		// Assign the main database object to $this->db
 		$CI =& get_instance();
diff --git a/system/database/DB_utility.php b/system/database/DB_utility.php
index 52196b7..a5f174f 100644
--- a/system/database/DB_utility.php
+++ b/system/database/DB_utility.php
@@ -33,7 +33,7 @@
 	 * Grabs the CI super object instance so we can access it.
 	 *
 	 */
-	function __construct()
+	function CI_DB_utility()
 	{
 		// Assign the main database object to $this->db
 		$CI =& get_instance();
diff --git a/system/database/drivers/odbc/odbc_driver.php b/system/database/drivers/odbc/odbc_driver.php
index bcd7937..08cd27b 100644
--- a/system/database/drivers/odbc/odbc_driver.php
+++ b/system/database/drivers/odbc/odbc_driver.php
@@ -48,9 +48,9 @@
 	var $_random_keyword;
 
 
-	function __construct($params)
+	function CI_DB_odbc_driver($params)
 	{
-		parent::__construct($params);
+		parent::CI_DB_driver($params);
 
 		$this->_random_keyword = ' RND('.time().')'; // database specific random keyword
 	}