ast modifs and additional arrow_taint phase to retrieve which arrow "protects" / "taints" which variable

- Renamed Mpfr to lustrec_mpfr
- Introduced dependency in Zarith. Trying to move away from Num

[bug cavale 93] solved: issue when resetting a stateless node. Now generating a warning and forcing the stateful status. Could be improved to remove the reset statement. (TODO)

- Bugs in partial evaluation for equalities among bool constants
  and a nice recursive call generating a stack overflow! Now solved
- Setup a timeout for z3 in seal
- Better log for seal

Contract resolution still need to be done as well as dealing with the machine code level and so on.

     package using it. It required a lot of refactoring.

node_Table hashtbl is now only available through functions of the corelang.mli

Moved lusic to .h printer after normalizing in case we want one day to produce ACSL from a normalized spec
Trying also to extend the parser to deal with imported nodes....

Different parsers yet but shared process.
In case of lusi input the C backend is bypassed since the .h is generated from the lusic and no C code should be generated since it may overwrite existing manually written code

But

- Modules now is more integrated and performed the building of the type/clock env.
  previously some computation were performed twice by different functions. Some of these functions have been moved from compiler_common to modules

- Contract were extended with list of statements.

- Adapted the parsing of specification with a cocospec compatible one
- The data structure of contracts is now almost cocospec compatible
- Lustrec-test has been updated to use the newest syntax

- arrow.ml* to define basic builder for arrow (node, name, ...)
- machine_code_common similar to corelang but for machine_code (printers, some builders, ...)
- machine_code restricted to the translatation from normalized nodes to machines

- Renamed type declarations as lustre_types and machine_code_types

- program type renamed as program_t
- Initiating the lustrev tool with dependencies to z3 and seal.