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This will allow transformations to apply use and clone.
Also, this will allow to simplify the driver structure.
Memoisation modulo env/clone/use requires some further 
adaptation (but this would be needed anyway).

  as it is most often ignored
- check for empty map in t_subst/f_subst
- bugfix: don't forget nested match statements in Decl and Compile_match

- check pattern well-formedness in Pattern
- add arguments to exceptions in Ty and Term

(unusable so far, must eliminate match statements, too)

- do not add to the new namespace the old instantiated names
- namespaces with the same name are merged instead of raising
  an exception.

Attention: examples clash_namespace1.why, already_theory1.why,
already_theory2.why, clash_type6.why, clash_type7.why migrated 
from bench/typing/bad/ to bench/typing/good/. Please, consult
these files and make sure you comprehend and approve the new
semantics.

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for uniquely tagged objects.

   - Util : Ajout de Creation generique de Set,Map et Hashtbl 
            quand on a un tag et une egalitée physique
   - Hashweak : Implementation de l'idee de Jean-Christophe et Andreï
   - Register : Simplification des types comme demandé par Jean-Christophe
                Mise à jour des fichiers qui en dépendait
   - Theory   : Ajout d'une facilité de création des th_inst
   - Encoding_decorate : Prelude pour l'encodage de Stéphane en utilisant flat_theory d'Andreï
   - Ty : Ajout de Sty, Mty et Hty
   - Main : Reduction de la taille des lignes à 80 colonnes

coming to you late in the evening and talking French.