Remove dead code written for PHP 5.2
diff --git a/system/core/CodeIgniter.php b/system/core/CodeIgniter.php
index 70f33d5..22072e9 100644
--- a/system/core/CodeIgniter.php
+++ b/system/core/CodeIgniter.php
@@ -416,11 +416,7 @@
 			$params = array($method, array_slice($URI->rsegments, 2));
 			$method = '_remap';
 		}
-		// WARNING: It appears that there are issues with is_callable() even in PHP 5.2!
-		// Furthermore, there are bug reports and feature/change requests related to it
-		// that make it unreliable to use in this context. Please, DO NOT change this
-		// work-around until a better alternative is available.
-		elseif ( ! in_array(strtolower($method), array_map('strtolower', get_class_methods($class)), TRUE))
+		elseif ( ! is_callable(array($class, $method)))
 		{
 			$e404 = TRUE;
 		}