This fixes an oversight in commit d91e5686.  Some of the views created for
Win32 child windows were being left out of any view hierarchy.  OpenGL contexts
attached to such child windows and views were not able to render to screen,
leaving blank areas.
Signed-off-by: Ken Thomases <ken@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>