Disable autoloader call from class_exists() occurences to improve performance

Note: The Driver libary tests seem to depend on that, so one occurence in CI_Loader is left until we resolve that.
diff --git a/system/core/CodeIgniter.php b/system/core/CodeIgniter.php
index cb4b735..7f76977 100644
--- a/system/core/CodeIgniter.php
+++ b/system/core/CodeIgniter.php
@@ -263,7 +263,7 @@
 	$class  = $RTR->fetch_class();
 	$method = $RTR->fetch_method();
 
-	if ( ! class_exists($class) OR $method[0] === '_' OR method_exists('CI_Controller', $method))
+	if ( ! class_exists($class, FALSE) OR $method[0] === '_' OR method_exists('CI_Controller', $method))
 	{
 		if ( ! empty($RTR->routes['404_override']))
 		{
@@ -272,7 +272,7 @@
 				$method = 'index';
 			}
 
-			if ( ! class_exists($class))
+			if ( ! class_exists($class, FALSE))
 			{
 				if ( ! file_exists(APPPATH.'controllers/'.$class.'.php'))
 				{
@@ -310,7 +310,7 @@
 				$method = 'index';
 			}
 
-			if ( ! class_exists($class))
+			if ( ! class_exists($class, FALSE))
 			{
 				if ( ! file_exists(APPPATH.'controllers/'.$class.'.php'))
 				{
diff --git a/system/core/Common.php b/system/core/Common.php
index f8c1290..ee9bb2e 100644
--- a/system/core/Common.php
+++ b/system/core/Common.php
@@ -149,7 +149,7 @@
 			{
 				$name = $prefix.$class;
 
-				if (class_exists($name) === FALSE)
+				if (class_exists($name, FALSE) === FALSE)
 				{
 					require_once($path.$directory.'/'.$class.'.php');
 				}
@@ -163,7 +163,7 @@
 		{
 			$name = config_item('subclass_prefix').$class;
 
-			if (class_exists($name) === FALSE)
+			if (class_exists($name, FALSE) === FALSE)
 			{
 				require_once(APPPATH.$directory.'/'.config_item('subclass_prefix').$class.'.php');
 			}
diff --git a/system/core/Hooks.php b/system/core/Hooks.php
index 17f6a02..b3b1119 100644
--- a/system/core/Hooks.php
+++ b/system/core/Hooks.php
@@ -195,7 +195,7 @@
 		// Call the requested class and/or function
 		if ($class !== FALSE)
 		{
-			if ( ! class_exists($class))
+			if ( ! class_exists($class, FALSE))
 			{
 				require($filepath);
 			}
diff --git a/system/core/Loader.php b/system/core/Loader.php
index 9306a09..6e5b58b 100644
--- a/system/core/Loader.php
+++ b/system/core/Loader.php
@@ -270,7 +270,7 @@
 				continue;
 			}
 
-			if ($db_conn !== FALSE && ! class_exists('CI_DB'))
+			if ($db_conn !== FALSE && ! class_exists('CI_DB', FALSE))
 			{
 				if ($db_conn === TRUE)
 				{
@@ -280,7 +280,7 @@
 				$CI->load->database($db_conn, FALSE, TRUE);
 			}
 
-			if ( ! class_exists('CI_Model'))
+			if ( ! class_exists('CI_Model', FALSE))
 			{
 				load_class('Model', 'core');
 			}
@@ -1091,11 +1091,11 @@
 
 		if ($prefix === '')
 		{
-			if (class_exists('CI_'.$class))
+			if (class_exists('CI_'.$class, FALSE))
 			{
 				$name = 'CI_'.$class;
 			}
-			elseif (class_exists(config_item('subclass_prefix').$class))
+			elseif (class_exists(config_item('subclass_prefix').$class, FALSE))
 			{
 				$name = config_item('subclass_prefix').$class;
 			}
@@ -1110,7 +1110,7 @@
 		}
 
 		// Is the class name valid?
-		if ( ! class_exists($name))
+		if ( ! class_exists($name, FALSE))
 		{
 			log_message('error', 'Non-existent class: '.$name);
 			show_error('Non-existent class: '.$name);
diff --git a/system/core/Output.php b/system/core/Output.php
index a208414..25ecd49 100644
--- a/system/core/Output.php
+++ b/system/core/Output.php
@@ -395,7 +395,7 @@
 		global $BM, $CFG;
 
 		// Grab the super object if we can.
-		if (class_exists('CI_Controller'))
+		if (class_exists('CI_Controller', FALSE))
 		{
 			$CI =& get_instance();
 		}