Fix a problem with the culling of out-of-range random objects. When

Fix a problem with the culling of out-of-range random objects.  When
the triangles containing the objects were out of the view Frustum,
they were never traversed by ssg (and thus, never culled).  Now, every
200 frames, do a pass through the whole scene graph with cull-testing
disabled and without drawing anything; that will allow random-objects
to be collected incrementally.