Pulling in Core Location now for compatibility.  Upgraded the remaining 4f matrix logic to 4d.  Added a real geocentric display adapter..  Not really using it yet.  Loft layer can now do outlines around the top of lofts.  Added screen importance calculation that takes solids into account.  Can now force renderer to set up again. Added new billboard layer, only useful in true 3D mode.  Cleaned up the backface checking logic in the view tracker, screen space generator and layout layer (finally).  Core leak in the tile quad loader.