GitLab

- hide the closure variable
- split t_app_beta into t_func_app_beta, which returns terms,
  and t_pred_app_beta which returns formulas

Also:
- check for non-recursivity in t_open_lambda
- implement t_is_lambda via t_open_lambda (less efficient,
  but the correct code without opening would be horrendous)
- drop t_app_lambda, subsumed by t_[func|pred]_app_beta
- support nested lambdas in t_[func|pred]_app_beta

Two points for discussion:

- t_lambda accepts both terms and formulas for the body.
  Thus, t_open_lambda, t_app_lambda, and t_app_beta can all
  return a term or a formula, depending on what is inside
  the lambda term. The caller should not forget to check.
  We could, in principle, always return a term (bool-typed
  when needed), which would exclude a possible run-time error,
  but then a caller who expects a formula, would have to
  recognize the results of the form [if f then True else False],
  before blindly attaching [== True] to them. Maybe still worth it:
  it's better if a forgotten check leads to an inefficient formula
  than to a type-checking error.

- t_lambda takes a preid which will be the binding variable in the
  produced epsilon. This permits us to give names to our lambdas
  if we want it (what for?) and to give locations to intermediate
  terms inside the epsilon. Overall, it's not very useful and can
  probably be removed.

"Never be clever for the sake of being clever." Glenn Gould

The type-checking benefits of separation of the ity and region types
are more important than the weight of extra functions to manipulate
a second type.

these generalize numerous type-specific X_all and X_any functions.
These are now defined as [Util.all X_fold] or [Util.any X_fold].

moved from map.why to bv.why + new theories BV31, BV63, and BV64
modules mach.int.Int32 etc. now have to_bv / of_bv routines
ocaml driver identify integers and bit vectors and makes use of
operations such as land

(no yet displayed in IDE)