Improved the debugger to work better with PPAS <= 9.2

Resolved the issues listed below:
- Function/Procedure (plpgsql/edb-spl) execution completed with an error - "no
  target for SPL-style OUT parameter" (PPAS <= 9.2)
  Invoke the target (procedure/function) with the value explicitly, instead of
  using the PQexecParams (a libpq API) due to a bug in PPAS <= 9.2
- A function with the OUT parameter and other VARIADIC parameter is not
  debuggable on PPAS/PostgreSQL
  Fixed it by using the sequence number properly for IN/INOUT parameters and
  ignoring them for the OUT parameter
- On execution completion an edb-spl function was showing result value with
  PPAS <= 9.2
  With the latest redesing of debugger, we were able to show the result
  properly for PPAS >= 9.3. But - for earlier version, we will have to use the
  anonymous block with edb-spl. And, that forced us to fetch the result as
  message and the result will be shown in the dbms-message window, instead of
  result window.
- Marker, showing current position of the execution in debugger, was offset by
  1 for PG/PPAS <= 9.0