message: Remove Changeset's explicitly default/deleted constructors
diff: @@ -22,12 +22,6 @@ struct Changeset {
  using file_ident_type = uint_fast64_t;
  using version_type = uint_fast64_t; // FIXME: Get from `History`.
  - Changeset() = default;
  - Changeset(Changeset&&) = default;
  - Changeset& operator=(Changeset&&) = default;
  - Changeset(const Changeset&) = delete;
  - Changeset& operator=(const Changeset&) = delete;
  -
  InternString intern_string(StringData); // Slow!
  InternString find_string(StringData) const noexcept; // Slow!
  StringData string_data() const noexcept;
  