message: das.cli: Reduce symbol size by dropping unused template argument.
diff: @@ -219,7 +219,7 @@ namespace das
  {}
  };
  - template <typename Formal, typename Default = void>
  + template <typename Default = void>
  class Value
  : public std::conditional_t<
  std::is_same<Default, void>::value,
  @@ -486,9 +486,9 @@ namespace das
  ELLE_ATTRIBUTE_R(bool, set);
  };
  - template <typename Formal, typename Default>
  + template <typename Default>
  std::ostream&
  - operator <<(std::ostream& out, Value<Formal, Default> const& v)
  + operator <<(std::ostream& out, Value<Default> const& v)
  {
  elle::fprintf(out, "Value(\"%s\", %s, %s)",
  v.option(), v.values(), v.set() ? "explicit" : "implicit");
  @@ -629,7 +629,7 @@ namespace das
  [&] (auto head, auto def)
  {
  using Default = typename decltype(def)::type;
  - using V = Value<typename decltype(head)::type, Default>;
  + using V = Value<Default>;
  if (flag)
  return V(p.defaults, Head::name(), pos, args,
  true, counter, set);
  @@ -645,7 +645,7 @@ namespace das
  },
  [&] (auto head, auto)
  {
  - using V = Value<typename decltype(head)::type, void>;
  + using V = Value<void>;
  if (flag)
  return V(0, Head::name(), pos, args, true, counter, set);
  else
  