Merge pull request #9028 from alalek:dnn_experimental_namespace

diff --cc modules/dnn/src/caffe/caffe_importer.cpp
index 7c33812,3f61310..c075651
--- 1/modules/dnn/src/caffe/caffe_importer.cpp
--- 2/modules/dnn/src/caffe/caffe_importer.cpp
+++ b/modules/dnn/src/caffe/caffe_importer.cpp
@@@ -40,10 -40,8 +40,8 @@@
  //M*/
  
  #include "../precomp.hpp"
- using namespace cv;
- using namespace cv::dnn;
  
 -#if HAVE_PROTOBUF
 +#ifdef HAVE_PROTOBUF
  #include "caffe.pb.h"
  
  #include <iostream>

diff --cc modules/dnn/src/dnn.cpp
Simple merge

diff --cc modules/dnn/src/init.cpp
Simple merge

diff --cc modules/dnn/src/precomp.hpp
Simple merge

diff --cc modules/dnn/src/tensorflow/tf_importer.cpp
index 592dc99,8a39d7b..7797fa7
--- 1/modules/dnn/src/tensorflow/tf_importer.cpp
--- 2/modules/dnn/src/tensorflow/tf_importer.cpp
+++ b/modules/dnn/src/tensorflow/tf_importer.cpp
@@@ -10,10 -10,8 +10,8 @@@ Implementation of Tensorflow models par
  */
  
  #include "../precomp.hpp"
- using namespace cv;
- using namespace cv::dnn;
  
 -#if HAVE_PROTOBUF
 +#ifdef HAVE_PROTOBUF
  #include "graph.pb.h"
  
  #include <iostream>

diff --cc modules/dnn/src/torch/torch_importer.cpp
Simple merge