C++: Add constructor and destructor for vector to IR test

Author: jketema

cpp/ql/test/library-tests/ir/ir/PrintAST.expected

@@ -1065,6 +1065,8 @@ struct vector {
         bool operator!=(iterator right) const;
     };
 
+    vector(T);
+    ~vector();
     iterator begin() const;
     iterator end() const;
 };