Description:
------------
I think mssql_execute() should return FALSE (or throw an ErrorException) when RAISERROR() raises error with severity >= mssql_min_error_severity().

Now it returns TRUE if query is run with success, no matter if error is risen.

Test script:
---------------
CREATE PROCEDURE MySP
BEGIN
  RAISERROR('Error happened', 18, 1)
END

<?php
$conn = mssql_connect(...);
mssql_min_error_severity(10);

$stmt = mssql_init('MySP', $conn);
if (($ret = mssql_execute($stmt)) == false)
{
  echo "Error!";
}
else
{
  echo "OK!";
}
?>

Expected result:
----------------
I expect the script to output "Error!".

Actual result:
--------------
That would output "OK!".