Fix build of various backends

modules/core/src/gl_core_3_1.cpp

@@ -2,6 +2,7 @@
 #include <sstream>
 #include "cvconfig.h"
 #include "opencv2/core.hpp"
+#include "opencv2/core/utility.hpp"
 #include "gl_core_3_1.hpp"
 
 #ifdef HAVE_OPENGL

modules/highgui/src/window_QT.cpp

@@ -949,7 +949,7 @@ void GuiReceiver::showImage(QString name, void* arr)
         mat = cvGetMat(arr, &stub);
 
         cv::Mat im(mat);
-        cv::imshow(name.toStdString(), im);
+        cv::imshow(name.toUtf8().data(), im);
     }
     else
     {