Description:
------------
It is trouble in "mb_convert_encoding" function.
"mb_convert_encoding($message, 'JIS', 'auto');" is failed.
"mb_convert_encoding($message, 'JIS', 'EUC-JP');" is not trouble. 

In php.ini, "mbstring.detect_order" is not set. 
";mbstring.detect_order = auto"

It is unquestionable in php-4.3.10.


Reproduce code:
---------------
<?php
$message = "??";
$message = mb_convert_encoding($message, 'JIS', 'auto');
print ($message);
?>

Expected result:
----------------
??

Actual result:
--------------
?