Description:
------------
Using MySQL math functions through PDO seems to throw a bothersome error that is not thrown when using the traditional mysql extension or by running the query directly on the database.

Using AVG or SUM in PDO throws mysql error 2036

"Fatal error: Uncaught exception 'PDOException' with message 'SQLSTATE[HY000]: General error: 2036..."

This has been confirmed to work with a standard conection using mysql_connect(), mysql_select_db(), mysql_query(), and mysql_fetch_array()

Reproduce code:
---------------
CREATE TABLE `MemberRating` (
  `MemberRatingId` int(11) NOT NULL auto_increment,
  `ContentEntryInfoId` int(11) default NULL,
  `value` int(11) default NULL,
  PRIMARY KEY  (`MemberRatingId`)
);

//add in several random numeric values for the
//ContentEntryInfoId of 191

$query = 'SELECT AVG(value) FROM MemberRating WHERE ContentEntryInfoId = 191';

$dbh = new PDO($dsn, $user, $password);
$sth = $dbh->prepare($query);
$sth->execute();
$result = $sth->fetchAll(PDO::FETCH_ASSOC);
print_r($result);

Expected result:
----------------
Array
(
    [0] => Array
        (
            [avg(value)] => 3.2000
        )

)

Actual result:
--------------
Fatal error: Uncaught exception 'PDOException' with message 'SQLSTATE[HY000]: General error: 2036 '