remove user-defined copy assign/constructor in favour of implicitly-defined ones

dune/common/parallel/indexset.hh

@@ -264,16 +264,6 @@ namespace Dune
         : Father(father), indexSet_(&indexSet)
       {}
 
-      iterator(const iterator& other)
-        : Father(other), indexSet_(other.indexSet_)
-      {}
-
-      iterator& operator==(const iterator& other)
-      {
-        Father::operator==(other);
-        indexSet_ = other.indexSet_;
-      }
-
     private:
       /**
        * @brief Mark the index as deleted.