using argv[0] represent binary executable files' name in help() function

in sample codes instead of cpp files' name.

samples/cpp/fback.cpp

@@ -8,14 +8,14 @@
 using namespace cv;
 using namespace std;
 
-static void help()
+static void help(char** argv)
 {
     cout <<
             "\nThis program demonstrates dense optical flow algorithm by Gunnar Farneback\n"
             "Mainly the function: calcOpticalFlowFarneback()\n"
             "Call:\n"
-            "./fback\n"
-            "This reads from video camera 0\n" << endl;
+        <<  argv[0]
+        <<  "This reads from video camera 0\n" << endl;
 }
 static void drawOptFlowMap(const Mat& flow, Mat& cflowmap, int step,
                     double, const Scalar& color)
@@ -35,11 +35,11 @@ int main(int argc, char** argv)
     cv::CommandLineParser parser(argc, argv, "{help h||}");
     if (parser.has("help"))
     {
-        help();
+        help(argv);
         return 0;
     }
     VideoCapture cap(0);
-    help();
+    help(argv);
     if( !cap.isOpened() )
         return -1;