message: Add deduction guides for vector tree iterator classes
diff: @@ -95,6 +95,10 @@ class VectorTreeLeavesIterator
  }
  };
  +template <typename VectorTreeType>
  +VectorTreeLeavesIterator(VectorTreeType*)
  + -> VectorTreeLeavesIterator<VectorTreeType>;
  +
  // Returns VectorTreeLeavesIterator range that spans all leaves of a tree.
  // Note that when the node passed as a tree is a leaf, the returned range spans
  // this node.
  @@ -135,6 +139,10 @@ class VectorTreePreOrderIterator
  }
  };
  +template <typename VectorTreeType>
  +VectorTreePreOrderIterator(VectorTreeType*)
  + -> VectorTreePreOrderIterator<VectorTreeType>;
  +
  // Returns VectorTreePreOrderIterator range that spans all nodes of a tree
  // (including the tree's root).
  template <typename VectorTreeType>
  @@ -170,6 +178,10 @@ class VectorTreePostOrderIterator
  this_type end() const { return this_type(_NextNode(this->node_)); }
  };
  +template <typename VectorTreeType>
  +VectorTreePostOrderIterator(VectorTreeType*)
  + -> VectorTreePostOrderIterator<VectorTreeType>;
  +
  // Returns VectorTreePostOrderIterator range that spans all nodes of a tree
  // (including the tree's root).
  template <typename VectorTreeType>
  