message: make size() functions const
diff: @@ -198,7 +198,7 @@ namespace ranges
  struct any_input_view_interface<Ref, true>
  : any_input_view_interface<Ref, false>
  {
  - virtual std::size_t size() = 0;
  + virtual std::size_t size() const = 0;
  };
  template<typename Ref>
  @@ -259,7 +259,7 @@ namespace ranges
  }
  virtual Ref read() const override { return *current(); }
  virtual void next() override { ++current(); }
  - std::size_t size() // override-ish
  + std::size_t size() const // override-ish
  {
  return static_cast<std::size_t>(ranges::size(range()));
  }
  @@ -453,7 +453,7 @@ namespace ranges
  struct any_view_interface<Ref, Cat, true>
  : any_view_interface<Ref, Cat, false>
  {
  - virtual std::size_t size() = 0;
  + virtual std::size_t size() const = 0;
  };
  template<typename Ref, category Cat>
  @@ -493,7 +493,7 @@ namespace ranges
  {
  return detail::make_unique<any_view_impl>(range_box_t::get());
  }
  - std::size_t size() // override-ish
  + std::size_t size() const // override-ish
  {
  return static_cast<std::size_t>(ranges::size(range_box_t::get()));
  }
  