Fix issue where llSetCameraAtOffset() and llSetCameraEyeOffset() in non-root prims moved camera/focus to wrong position.

For non-root prim, eye offsets now need to be made relative to root prim if either camera-at or camera-eye are set.
Probably a regression since November 2013 when all sits were made relative to root prim to match viewer expections (and fix other bugs).
Addresses http://opensimulator.org/mantis/view.php?id=7176