Proof_usingUtility code for section variables handling in Proof using...
val definition_using : 
  Environ.env ->
  Evd.evar_map ->
  using:Vernacexpr.section_subset_expr ->
  terms:EConstr.constr list ->
  tProcess a using expression in definitions to provide the list of used terms
val name_set : Names.Id.t -> Vernacexpr.section_subset_expr -> unitval suggest_constant : Environ.env -> Names.Constant.t -> unitval suggest_variable : Environ.env -> Names.Id.t -> unitval get_default_proof_using : unit -> Vernacexpr.section_subset_expr optionval using_from_string : string -> Vernacexpr.section_subset_expr