qt_x11_wait_for_window_manager assumes ReparentNotify

in src/gui/kernel/qwidget_x11.cpp, qt_x11_wait_for_window_manager assumes that the WM reparents the windows. Most tiling WMs don't do that, since they have no window border, resulting in a 2 seconds delay for showFullscreen on those WMs.

Suggestion: remove the Reparent state, or skip over it, if there is a MapNotify/Expose in the queue already.