fixed some warnings

GPU: TargetArchs -> added FEATURE_SET prefix.

samples/cpp/squares.cpp

@@ -139,7 +139,7 @@ void drawSquares( Mat& image, const vector<vector<Point> >& squares )
 }
 
 
-int main(int argc, char** argv)
+int main(int /*argc*/, char** /*argv*/)
 {
     static const char* names[] = { "pic1.png", "pic2.png", "pic3.png",
         "pic4.png", "pic5.png", "pic6.png", 0 };