- move a few variables from SceneDrawer to FRenderViewpoint.
The global r_viewpoint variable is left alone now to always represent the current viewpoint to the play code.
The main reason behind this change is to reduce the amount of global variables being used by the hardware renderer's scene processing code.
Game code should never ever call the renderer directly. This must be done through the video interface so that it can also work with other framebuffers later.
