Fix unused arguments of Make1stOrderPerturbation

Change-Id: Ibc7ef45e88abdde67dbb2705a3423ad4c4594859

include/ceres/internal/autodiff.h

diff --git a/include/ceres/internal/autodiff.h b/include/ceres/internal/autodiff.h
index fe64e82..c796618 100644
--- a/include/ceres/internal/autodiff.h
+++ b/include/ceres/internal/autodiff.h
@@ -197,7 +197,7 @@
 template <int N, int Offset, typename T, typename JetT>
 struct Make1stOrderPerturbation<N, N, Offset, T, JetT> {
  public:
-  static void Apply(const T* src, JetT* dst) {}
+  static void Apply(const T* /* NOT USED */, JetT* /* NOT USED */) {}
 };
 
 // Calls Make1stOrderPerturbation for every parameter block.