rest of the modules. More precisely, the lucky tools now rely only on
Prog (see below), that is Lucky-agnostic.

The rationale is to ease the plug of a Lutin programs interpreter
afterwards. Indeed, one (ougth to) just need to implement its own
version of the Prog module.

To do that, I've splitted LusProg into :
   LucParse
   LucProg
   Prog

Then, I moved the content of Env_state into LucProg. And all this
had some consequences, that cause more code movement.