added constants.php file and implemented constants for file system modes
diff --git a/system/libraries/Output.php b/system/libraries/Output.php
index a4d8d34..07990eb 100644
--- a/system/libraries/Output.php
+++ b/system/libraries/Output.php
@@ -308,7 +308,7 @@
 		fwrite($fp, $expire.'TS--->'.$output);

 		flock($fp, LOCK_UN);

 		fclose($fp);

-		@chmod($cache_path, 0777);

+		@chmod($cache_path, DIR_WRITE_MODE);

 

 		log_message('debug', "Cache file written: ".$cache_path);

 	}