Fixed few warnings on Linux

Author: Andrey Kamaev

modules/highgui/src/cap_gstreamer.cpp

@@ -274,7 +274,7 @@ void CvCapture_GStreamer::removeFilter(const char *filter)
 //
 // connect uridecodebin dynamically created source pads to colourconverter
 //
-void CvCapture_GStreamer::newPad(GstElement *uridecodebin,
+void CvCapture_GStreamer::newPad(GstElement * /*uridecodebin*/,
                              GstPad     *pad,
                              gpointer    data)
 {

modules/highgui/src/window_gtk.cpp

@@ -678,6 +678,8 @@ double cvGetOpenGlProp_GTK(const char* name)
     result = window->useGl;
 
     __END__;
+#else
+    (void)name;
 #endif
 
     return result;
@@ -1004,6 +1006,8 @@ static gboolean cvImageWidget_expose(GtkWidget* widget, GdkEventExpose* event, g
         drawGl(window);
         return TRUE;
     }
+#else
+    (void)data;
 #endif
 
   CvImageWidget *image_widget;