cmLinkedTree: avoid unnecessary copies during Push of T

Source/cmLinkedTree.h

@@ -137,7 +137,7 @@ public:
 
   iterator Push(iterator it) { return Push_impl(it, T()); }
 
-  iterator Push(iterator it, T t) { return Push_impl(it, t); }
+  iterator Push(iterator it, T t) { return Push_impl(it, std::move(t)); }
 
   bool IsLast(iterator it) { return it.Position == this->Data.size(); }
 
@@ -177,12 +177,12 @@ private:
 
   T* GetPointer(PositionType pos) { return &this->Data[pos]; }
 
-  iterator Push_impl(iterator it, T t)
+  iterator Push_impl(iterator it, T&& t)
   {
     assert(this->UpPositions.size() == this->Data.size());
     assert(it.Position <= this->UpPositions.size());
     this->UpPositions.push_back(it.Position);
-    this->Data.push_back(t);
+    this->Data.push_back(std::move(t));
     return iterator(this, this->UpPositions.size());
   }