move pointer to .rodata

Signed-off-by: Rémi Duraffort <ivoire@videolan.org>

modules/gui/qt4/components/preferences_widgets.cpp

@@ -214,7 +214,7 @@ void InterfacePreviewWidget::setPreview( int comboid )
     /* Need to move resources references as soon as qt4.cpp
        local defines has been moved somewhere else
     */
-    char * pixmaps[] = { ":/prefsmenu/sample_classic",
+    const char * pixmaps[] = { ":/prefsmenu/sample_classic",
                                ":/prefsmenu/sample_complete",
                                ":/prefsmenu/sample_minimal" };
     setPixmap( QPixmap( pixmaps[ comboid ] ) );