Fix compile

Author: mariusmuja

src/cpp/flann/algorithms/kdtree_cuda_3d_index.h

@@ -273,6 +273,17 @@ class KDTreeCuda3dIndex : public NNIndex<Distance>
     {
     }
 
+protected:
+    void buildIndexImpl()
+    {
+        /* nothing to do here */
+    }
+
+    void freeIndex()
+    {
+        /* nothing to do here */
+    }
+
 private:
 
     void uploadTreeToGpu( );