Revision 43

The end of the attempt to implement recursively defined types. After this point, all the files are cleared away and retyped with new assumptions in mind.

Note from wiki: I've decided to give up on recursively defined types. Getting the iterators right involves too much copying of indexes (to unwind-protect). The use-case, trees, can be implemented using pointers, once I add pointers. Without recursively defined types, there's no advantage to "recursive counters" over "Arrow style" (see paper), so I'm going to focus on "Arrow style" only.