Get Position (22)
        +--------------------------------------------------------------------+
        |  Operation  | Position |DataBuffer| DataBuff |    Key   |    Key   |
        |             |  Block   |          |  Length  |   Buffer |   Number |
+-------+-------------+----------+----------+----------+----------+----------|
|Expects|  BT_GET_POS |    X     |          |          |          |          |
|-------+-------------+----------+----------+----------+----------+----------|
|Returns|             |    X     |  Address |  Length  |          |          |
+----------------------------------------------------------------------------+

Gets the 4 byte offset of the current record.

This offset may be used with the Get Direct operation to quickly get to
the selected record.