Description:
------------
function strtolower doesn't work good

when try to lower Czech characters (with diacritics) written in utf-8 





Reproduce code:
---------------
try this

setlocale(LC_ALL, "cs_CZ.utf8");
$str = "?̊?؎?????ύ??";
echo strtolower($str);

// correct output is: 
//      ???????????????
// but you will see something else



Expected result:
----------------
correct function

Actual result:
--------------
see example above