* This will allow for later additions of more complex tests.

* Introduces a specialization that fulfills the old interface.

* It is allowed to be NULL when no data is passed on a process.

* Since we don't use MPI_Put this might improve performance.

* This also fixes a previously introduced memory leak.

* This will enable functions in pio_interface later to be written
  without regard for header specifics.

* This allows to have the offset entry available for all types.

* This ensures a consistent traversal on all I/O tasks.

* This ensures synchronization.