diag_hand_yaw and diag_hand_pitch turn the synthetic hands' aim from the head's,
so the menu laser can be pointed. vr-state.txt says where the cursor is (u, v and
the pixel in the screen image). analyze_roll.py compares HUD-on and HUD-off dumps at
different rolls and says how far the world and the HUD turned. Host test for the
laser maths (ray against the quad, beam and dot poses).
