Some cleanup related to mt_rand()

- min and max values are 0 and mt_getrandmax() by default
- remove useless mt_srand() seed calls
diff --git a/system/core/Common.php b/system/core/Common.php
index efa7a93..b4f0c38 100644
--- a/system/core/Common.php
+++ b/system/core/Common.php
@@ -92,7 +92,7 @@
 		 */
 		if (is_dir($file))
 		{
-			$file = rtrim($file, '/').'/'.md5(mt_rand(1,100).mt_rand(1,100));
+			$file = rtrim($file, '/').'/'.md5(mt_rand());
 			if (($fp = @fopen($file, FOPEN_WRITE_CREATE)) === FALSE)
 			{
 				return FALSE;