Remove use of more deprecated Qt functions, disable deprecation warnings

* Unfortunately at least one deprecated function
  QDesktopWidget::screenGeometry(const QPoint &p) has no easy alternative that
  works on 5.9 which is the version we have available by default on windows.

qrenderdoc/Windows/Dialogs/VirtualFileDialog.cpp

@@ -496,7 +496,7 @@ public:
     return qMin(maxColCount, sourceModel()->columnCount(parent));
   }
 
-  void refresh() { QSortFilterProxyModel::filterChanged(); }
+  void refresh() { QSortFilterProxyModel::invalidateFilter(); }
   int maxColCount = INT_MAX;
   bool showFiles = true;
   bool showDirs = true;