Drawables,StateSet, and osgDB::Registry.
Added cleanup_frame() from to osgProducer::OsgCamerGroup to help with proper
clean of OpenGL objects before exit, and modified osgviewer, osghangglider,
osgwindows examples to do the extra frame call to cleanup_frame() before exit.
Made Matrix be a typedef to either Matrixf or Matrixd. Defaults to Matrixf.
Converted the osgGA::MatrixManipulators and osgProducer::Viewer/OsgCameraGroup
across to using exclusively Matrixd for internal computations and passing betwen
Manipulators, Producer and SceneView. Note, SceneView still uses Matrix internally
so will depend on what is set as the default in include/osg/Matrix.
Added the ability to osgProducer::setDone/getDone(), kept done() as the
method that the viewer main loop uses for detecting the exit condition.
