Gui: Use auto and range-based for (#7481)

* On lines where the variable type is obvious from inspection, avoid repeating the type using auto. 
* When possible use a ranged for loop instead of begin() and end() iterators

src/Gui/WaitCursor.cpp

@@ -107,10 +107,10 @@ bool WaitCursorP::isModalDialog(QObject* o) const
             parent = QWidget::find(window->winId());
     }
     while (parent) {
-        QMessageBox* dlg = qobject_cast<QMessageBox*>(parent);
+        auto dlg = qobject_cast<QMessageBox*>(parent);
         if (dlg && dlg->isModal())
             return true;
-        QProgressDialog* pd = qobject_cast<QProgressDialog*>(parent);
+        auto pd = qobject_cast<QProgressDialog*>(parent);
         if (pd)
             return true;
         parent = parent->parentWidget();