Call Layout() after DrawingPanel OnSize event

When processing the `OnSize` event in the `GameArea` and calling the
embedded `DrawingPanel` `OnSize` event, call `Layout()` afterwards.

This seems to improve the resizing behavior of the EGL `wxGLCanvas`
`DrawingPanel` on Wayland.

Signed-off-by: Rafael Kitover <rkitover@gmail.com>

src/wx/panel.cpp

@@ -1381,6 +1381,7 @@ void GameArea::OnSize(wxSizeEvent& ev)
     // panel may resize
     if (panel)
         panel->OnSize(ev);
+    Layout();
 
     ev.Skip();
 }