Description:
------------
mssql_fetch_* returns 0 instead of NULL when the datatype is "bit".



Reproduce code:
---------------
<?php
$conn = mssql_connect($src, $uid, $pwd);
mssql_select_db($db_name);
$sql = "SELECT Cast (Null as Bit) As Should_Be_Null,"
     . "       Cast (0 as Bit)    AS Should_Be_Int_0,"
     . "       Cast (1 as Bit)    As Should_Be_Int_1";
$result = mssql_query($sql);
return mssql_fetch_array($result);
?>



Expected result:
----------------
Should return (NULL, 0, 1)

Actual result:
--------------
returns (0, 0, 1)