Things that are currently broken:
- the ability to init vars in the dot
- controling the name of local vars in the rif output

The idea is to use the Obj module (arg !!!), which is safe thanks to
the fact that there is now only one register function, which forces all the
'v to be bound to the same type.

But I bumped into the "value restriction" limitation
https://stackoverflow.com/questions/22507448/the-value-restriction

Indeed, I need to store functions of 'v in some tables (or references),

And tables are necessaryly weakly polymorphic !

https://v1.realworldocaml.org/v1/en/html/imperative-programming-1.html#side-effects-and-weak-polymorphism

Indeed, by using the Env.nset and Env.nget defined in
0d6575a7 a pb that was hided by the
use of Env.set and Env.get was triggered.

The bug was that variables initialisations were done several times.

In sasa.ml, the way I was updating the Env.t by iterating on the
variables was forcing to "close" expressions that were calling init
functions.

More precisely, they were not consistent by the behavior of -custd mode.
Indeed, It was returning the values of variables after the step is performed.

In the custom demon mode, sasa returns Enab and variable values before
the Activate is computed by the demon.

Chosing one behavior or the other is arguable ; the main advantage of
this choice is that we don't miss the initial values.

The rationale is that
 - it is not always the cmxs that is necessary .e.g., rdbg uses .cma or .ml
 - it makes more sense to refer to the source code

This can be used from rdbg from example, to generate session files.

In particular, 'rdbg -lurette' now works thanls to this option
(cf rdbg sha 63566a893807361691137cafe15854a2a7395eec)

Remove the --generate-rdbg-load one that is less general

Save/restore the PRGS at checkpoints (necessary for internal demons).

This is necessary because I cannot Dynlink .cmxs files from a ocaml
toplevel. Hence, one way to load the algos from rdbg is to
#load .cma files. This option generates an ocaml file that
can be #used by automatically generated rdbg-session.ml files.