Qt::WindowOverridesSystemGestures seems to only be useful in Wayland

It would be nice if

• The doc mentioned the applicability of the flag (apparently only here ; https://github.com/qt/qtwayland/blob/8e3c71b2d1ec37222bf1648aa23eb033062b4ea6/src/client/qwaylandextendedsurface.cpp )
• It was extended to prevent gestures like the swiping in Windows 10: currently setting a QtQuick application as full screen is not enough to ensure that it stays on top, and it is possible to swipe out of it.