attached patch modifies QT4Window to not derive from NativeWindow (but
from Window instead). It also brings the examples for rendering from the
GUI thread and for rendering from a separate thread into the QGLWidget
back to working condition (only tested on X11).
I believe the motivation for deriving from NativeWindow was the parallel
drawer that needs to be able to activate the context when needed, but
the proposed solution should keep that and seems neater than attempting
to capture the Qt created context with platform specific code.