support oracle cursor expressions in jdbc requests

This would allow creating nested XML structures.

select department_id, department_name,
cursor(select first_name, last_name
from employees e
where e.department_id = d.department_id) emps
from departments d

Would result in

 
<DEPARTMENT>               
  <DEPARTMENT_ID>20</DEPARTMENT_ID>
  <DEPARTMENT_NAME>Marketing</DEPARTMENT_NAME>
    <EMPS>
      <EMPS_ROW>
        <FIRST_NAME>Michael</FIRST_NAME>
        <LAST_NAME>Hartstein</LAST_NAME>
      </EMPS_ROW>
      <EMPS_ROW>
        <FIRST_NAME>Pat</FIRST_NAME>
        <LAST_NAME>Fay</LAST_NAME>
      </EMPS_ROW>
    </EMPS>
</DEPARTMENT>