message: Make size() return size_t
  It probably returns the biggest integer used in the whole module, it
  doesn't make sense that it uses a smaller type.
diff: @@ -197,7 +197,7 @@ class Bitmap_cubical_complex_base {
  /**
  * Returns number of all cubes in the data structure.
  **/
  - inline unsigned size() const { return this->data.size(); }
  + inline std::size_t size() const { return this->data.size(); }
  /**
  * Writing to stream operator. By using it we get the values T of cells in order in which they are stored in the
  