Beta-release of the CBS framework

The CBS library provides funcons for expressing and computing various kinds of values:

- algebraic datatypes:
- tuples
- lists (strings are lists of characters)
- vectors
- trees
- references (pointers are references or pointer-null)
- records
- variants
- classes
- objects
- bit-vectors

- sets
- maps
- multisets (bags)
- graphs (directed)

- abstractions (closures or dynamic)
- thunks (no argument)
- functions (single value argument)
- patterns (binding or failing)

- value-types (representing sets of values)

(Further kinds of values are provided in connection with particular kinds of computations.)

Funcons can take sequences of values as arguments, and compute sequences of values as results. The only sequences that are themselves values are trivial sequences of length one.

The absence of a computed value is represented by the empty sequence `( )`

.
Funcons that may compute `( )`

have result types of the form `T?`

, and
generally need to be preceded by `checked`

when used as arguments of other
funcons.