gtkwindow: Make sure to update the shadow width, opaque region and border windows...

gtkwindow: Make sure to update the shadow width, opaque region and border windows when realizing

Otherwise, they might not be properly set before the window is mapped.

For the opaque region and border window, it means that they won't get
set before the next size allocation, which tends to not be a bit deal.

For the shadow width, though, _GTK_FRAME_EXTENTS has a different meaning
when it's set before the window is mapped, so we need to make sure that
it's properly set when the window is mapped.