Mark unused parameters

Fix build for Ubuntu 16.04 where the compilation failed because of some
unused parameters.
To fix this I marked the unused a parameters in DummySearch the same way
it is done in other parts of the code.

test/features/test_normal_estimation.cpp

@@ -194,6 +194,8 @@ class DummySearch : public pcl::search::Search<PointT>
     virtual int nearestKSearch (const PointT &point, int k, std::vector<int> &k_indices,
                                 std::vector<float> &k_sqr_distances ) const
     {
+      (void)point;
+
       EXPECT_GE (k_indices.size(), k);
       EXPECT_GE (k_sqr_distances.size(), k);
 
@@ -203,6 +205,11 @@ class DummySearch : public pcl::search::Search<PointT>
     virtual int radiusSearch (const PointT& point, double radius, std::vector<int>& k_indices,
                               std::vector<float>& k_sqr_distances, unsigned int max_nn = 0 ) const
     {
+      (void)point;
+      (void)radius;
+      (void)k_indices;
+      (void)k_sqr_distances;
+
       return max_nn;
     }
 };