wumpus-basic

Copperbox revision 2256.

Initial work adding concat operations (cf. pretty print libs) to LocImage. I've rather overlooked that LocImage supports concat operations: AdvGraphic naturally supports them but so does LocImage if we just move the start point - LocImage is too primitive to account for a notion of border.

Some of the clunky chain operations in Wumpus-Drawing can be superseded by concat operations on LocImages and other moveable graphic objects.