Incorporate some of the advances from `tilttrack`.

* Set view context in the player HUD loop inside `ST_overlayDrawer()`.
* The HUD code now gets all interpolated camera data from the view context instead of half-heartedly recreating it.
* Move Lua HUDlib data to the view context system instead of an else ladder.
* View roll support in HUD tracking, because the other changes made this trivial.
* Remove old_viewrollangle as it is now redundant.