restored Parameters() constructor to maintain ABI compatibility. Added CV_EXPORTS to nested class

modules/objdetect/include/opencv2/objdetect/detection_based_tracker.hpp

@@ -59,16 +59,12 @@ namespace cv
 class CV_EXPORTS DetectionBasedTracker
 {
     public:
-        struct Parameters
+        struct CV_EXPORTS Parameters
         {
             int maxTrackLifetime;
             int minDetectionPeriod; //the minimal time between run of the big object detector (on the whole frame) in ms (1000 mean 1 sec), default=0
 
-            Parameters()
-            {
-                maxTrackLifetime=5;
-                minDetectionPeriod=0;
-            }
+            Parameters();
         };
 
         class IDetector

modules/objdetect/src/detection_based_tracker.cpp

@@ -578,6 +578,12 @@ bool cv::DetectionBasedTracker::SeparateDetectionWork::communicateWithDetectingT
     return shouldHandleResult;
 }
 
+cv::DetectionBasedTracker::Parameters::Parameters()
+{
+  maxTrackLifetime = 5;
+  minDetectionPeriod = 0;
+}
+
 cv::DetectionBasedTracker::InnerParameters::InnerParameters()
 {
     numLastPositionsToTrack=4;