GBT train/test was added to tree_engine sample

samples/c/tree_engine.cpp

@@ -37,6 +37,7 @@ int main()
     CvBoost boost;
     CvRTrees rtrees;
     CvERTrees ertrees;
+	CvGBTrees gbtrees;
 
     CvMLData data;
 
@@ -71,6 +72,10 @@ int main()
         printf("======ERTREES=====\n");
         ertrees.train( &data, CvRTParams( 10, 2, 0, false, 16, 0, true, 0, 100, 0, CV_TERMCRIT_ITER ));
         print_result( ertrees.calc_error( &data, CV_TRAIN_ERROR), ertrees.calc_error( &data, CV_TEST_ERROR ), ertrees.get_var_importance() );
+
+		printf("======GBTREES=====\n");
+		gbtrees.train( &data, CvGBTreesParams(CvGBTrees::DEVIANCE_LOSS, 100, 0.05f, 0.6f, 10, true));
+		print_result( gbtrees.calc_error( &data, CV_TRAIN_ERROR), gbtrees.calc_error( &data, CV_TEST_ERROR ), 0 );
     }
     else
         printf("File can not be read");