Qt6 port:

* Explicitly include some missing headers
* Use 'static const char*' for XPM icon
* Skip template parameters for qMakePair
* Constructor of QFileInfo is marked as 'explicit' now
* QString::fromLatin1() also accepts a QByteArray
* QDateTime::fromTime_t() is deprecated in Qt5 and has been removed in Qt6. Use QDateTime::fromSecsSinceEpoch()
* QDateTime::toTime_t() is deprecated in Qt5 and has been removed in Qt6. Use QDateTime::toSecsSinceEpoch()
* QApplication::globalStrut() is deprecated. Don't use it any more.
* QWidget::isTopLevel() is deprecated, use QWidget::isWindow()

src/Gui/Action.cpp

@@ -25,6 +25,7 @@
 
 #ifndef _PreComp_
 # include <QActionEvent>
+# include <QActionGroup>
 # include <QApplication>
 # include <QEvent>
 # include <QMenu>