Fresh Rust port of Fadec fadec-enc2.h and encode2.c.
Upstream: https://github.com/aengelke/fadec
Pinned revision: 3994d89500985491b1a7ccc17827a22058b3de49
Copyright (c) 2018, Alexis Engelke. BSD-3-Clause; see LICENSE.

The production build consumes the fresh tpde_fadec_gen Rust generator and
its pinned instruction table. C and Python references are test-only.
