Merge EvalType, EvalNode and EvalEq into a single module GetEff.

EvalNode.f -> GetEff.node,
EvalType.f -> GetEff.typ,
EvalEq.f -> GetEff.eq

EvalConst.f (val_exp -> const_eff list) should have been put there too,
but in fact EvalConst.f ougth to be splitted in two parts:
  - val_exp -> val_exp_eff (but this function already exist)
  - val_exp_eff -> const_eff list

Therefore, the signature of EvalConst.f will be changed to:
val_exp_eff -> const_eff list (and will use GetEff.val_exp)

Ditto for eval_array_index.

 eval_array_index : CompiledData.id_solver -> SyntaxTreeCore.val_exp -> int -> int

ougth to be splitted into two functions:
   - CompiledData.id_solver -> SyntaxTreeCore.val_exp_eff
   - SyntaxTreeCore.val_exp_eff -> int -> int

Ditto for eval_array_size

 eval_array_size : CompiledData.id_solver -> SyntaxTreeCore.val_exp -> int

ougth to be splitted into two functions:
   - CompiledData.id_solver -> SyntaxTreeCore.val_exp_eff
   - SyntaxTreeCore.val_exp_eff -> int

arg... evalConst.f est utilis par GettEff.typ !!!