fix PILE OF POO

Replaces a fragile relative-counter based implementation extents with an extra column of absolute table locations.  Now puts out correct "type 0" extents for plane 1.  Plane changes are forced to use a "type 1" gap extent even if the gap is only 1 big, so that the next plane gets a fresh start.  Saves all of 4 entries in the names table.  :)