wip/why 2.29 NetBSD

Why is a software verification platform.

This platform contains several tools:

1. a general-purpose verification condition generator (VCG), Why, which is
   used as a back-end by other verification tools (see below) but which
   can also be used directly to verify programs (see for instance these
   examples);
2. a tool Krakatoa for the verification of Java programs;
3. a tool Caduceus for the verification of C programs; note that Caduceus
   is somewhat obsolete now and users should turn to Frama-C instead.

One of the main features of Why is to be integrated with many existing provers (proof assistants such as Coq, PVS, Isabelle/HOL, HOL 4, HOL Light, Mizar and decision procedures such as Simplify, Alt-Ergo, Yices, Z3, CVC3, etc.).