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

use ghost variables instead of existential variables to avoid read / write capture problems with variable reuse

- 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

- real constants are hidden in Real.ml{i} module

[printer] more kind2 syntax

- now properly records the scopes
- only register requested ones

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

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

- a bug in regressio ntest Simulink/integrator_ext_IC_matrix_test revealed the following (serious issue):
  when building the list of instruction (in the machine code) the access to variable were hardcoded to LocalVar or StateVAr depending whether the variables was part of the identified memories.
  Un fortunately the set of memories is only known after iterating through all definitions. A read access to a memory which was scheduled before its update was generating a non compilable C code:
  the access to the memory x which should be written as mem->x was written as a local access "x". But x was not declared as a local variable: hence gcc compile error.

  The current commit is pretty involved. It goes through all the code:
  - LocalVar and StateVar have been merged in Var in machine instructions (rhs ie expressions)
  - any possible print or access to these shall be given access to the machine (ie its memories)
    so a lot of functions have been enriched with a machine first argument.

  Regression tests performed well showing no additional bug introduced.  The only Unstable->Broken changes are the DIFF which could not be run at all before.

Adapted the parser/types/constructors for cocospec 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

Structs defining machines are now in machine_code_types

- 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.

[general] large modification: added machine types, a second typing phase dealing with machine types (eg uint8)
          typing was transformed as a functor and parametrized by basic types (int/real/bool)
          it can also be applied multiple times on the same program