QShapedPixmapWindow incorrectly set at tooltip

The little window that shows the drag icon during drag and drops has an incorrect window type (at least on X11) as Tooltip
in its constructoore:
setFlags(Qt::ToolTip | Qt::FramelessWindowHint |
Qt::X11BypassWindowManagerHint | Qt::WindowTransparentForInput | Qt::WindowDoesNotAcceptFocus);

This may led window managers to mismanage it, as on X11 that window is supposed to have the type
_NET_WM_WINDOW_TYPE_DND