Add a real exception handler

Close #1590
Close #3200
diff --git a/system/core/CodeIgniter.php b/system/core/CodeIgniter.php
index e3d3a1f..88e730b 100644
--- a/system/core/CodeIgniter.php
+++ b/system/core/CodeIgniter.php
@@ -132,7 +132,8 @@
  *  Define a custom error handler so we can log PHP errors
  * ------------------------------------------------------
  */
-	set_error_handler('_exception_handler');
+	set_error_handler('_error_handler');
+	set_exception_handler('_exception_handler');
 	register_shutdown_function('_shutdown_handler');
 
 /*