fixed warning from GCC

samples/gpu/cascadeclassifier.cpp

@@ -1,5 +1,7 @@
 // WARNING: this sample is under construction! Use it on your own risk.
+#if defined _MSC_VER && _MSC_VER >= 1400
 #pragma warning(disable : 4100)
+#endif
 
 #include "cvconfig.h"
 #include <iostream>
@@ -14,7 +16,6 @@ using namespace std;
 using namespace cv;
 using namespace cv::gpu;
 
-
 #if !defined(HAVE_CUDA)
 int main(int argc, const char **argv)
 {