Merge pull request #3821 from asmorkalov:as/new_dnn_caffe

Do not use forward to layer feature in WeChat to support the new dnn engine

Author: asmorkalov

modules/wechat_qrcode/src/detector/ssd_detector.cpp

@@ -24,7 +24,7 @@ vector<Mat> SSDDetector::forward(Mat img, const int target_width, const int targ
                        false, false);
     net_.setInput(input, "data");
 
-    auto prob = net_.forward("detection_output");
+    auto prob = net_.forward();
     vector<Mat> point_list;
     // the shape is (1,1,100,7)=>(batch,channel,count,dim)
     for (int row = 0; row < prob.size[2]; row++) {
@@ -54,4 +54,4 @@ vector<Mat> SSDDetector::forward(Mat img, const int target_width, const int targ
     return point_list;
 }
 }  // namespace wechat_qrcode
-}  // namespace cv
+}  // namespace cv