Explicitly default ilistTest::Node's copy constructor

In the presence of a user-declared dtor, calling an implicit copy ctor
is deprecated in C++11.

llvm-svn: 231256

llvm/unittests/ADT/ilistTest.cpp

@@ -21,7 +21,8 @@ struct Node : ilist_node<Node> {
   int Value;
 
   Node() {}
-  Node(int _Value) : Value(_Value) {}
+  Node(int Value) : Value(Value) {}
+  Node(const Node&) = default;
   ~Node() { Value = -1; }
 };