Description:
------------
When you're connected to a database by PDO you are unable to execute a query which tries to run against another database within this connection by giving a correct database object name (database:sysmaster).
Rather than creating a second PDO instance it should be possible to run such queries.
This leads also to problems when trying to gather information from different databases in one query.

select table1.column,
table2.column
from database1:table1, database2:table2

How would you write such queries?

Reproduce code:
---------------
<?php
putenv('INFORMIXDIR=/home/informix');

echo "(1) database: stores_demo<br />\n";
$db = new PDO("informix:host=192.168.0.127;service=1536;database=stores_demo;server=ifx10;");
$db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$db->setAttribute(PDO::ATTR_CASE, PDO::CASE_LOWER);
$query = "select odb_dbname from sysmaster:sysopendb where odb_iscurrent = 'Y'";
echo "$query<br />\n";
try {
   $sql = $db->query($query);
   $sql->setFetchMode(PDO::FETCH_NAMED);
   var_dump($sql->fetch());
} catch (Exception $e) {
   echo $e->getMessage();
}
$db = null;
echo "<br />\n";
echo "<br />\n";

// // // // // // // // // // // // // // // // // // // // // // // // // // //

echo "(2) database: sysmaster<br />\n";
$db = new PDO("informix:host=192.168.0.127;service=1536;database=sysmaster;server=ifx10;");
$db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$db->setAttribute(PDO::ATTR_CASE, PDO::CASE_LOWER);
$query = "select odb_dbname from sysopendb where odb_iscurrent = 'Y'";
echo "$query<br />\n";
try {
   $sql = $db->query($query);
   $sql->setFetchMode(PDO::FETCH_NAMED);
   $dbsname = $sql->fetch();
   printf("result: %s<br />\n", $dbsname["odb_dbname"]);
} catch (Exception $e) {
   echo $e->getMessage();
}
$db = null;
?>


Expected result:
----------------
Both queries should return the actual selected database as specified by the DSN connection string.

Actual result:
--------------
(1) database: stores_demo
select odb_dbname from sysmaster:sysopendb where odb_iscurrent = 'Y'
SQLSTATE[42000]: Syntax error or access violation: -201 [Informix][Informix ODBC Driver][Informix]Unspecified System Error = -201. (SQLPrepare[-201] at /usr/local/src/php-5.2.3/ext/pdo_informix/informix_driver.c:131)

(2) database: sysmaster
select odb_dbname from sysopendb where odb_iscurrent = 'Y'
result: sysmaster