was the style of the old HUD, and it should be fully-compatible ...)
- remove erroneous <modulo> from f16.xml. This isn't even read there.
- enable nadir and zenith (they are just too pretty to ignore them :-)
- various tweaks
$ fgfs --aircraft=f16-3d --prop:hud=Huds/f16.xml --prop:sim/hud/visibility\[1\]=1
The hud path is for now expected in /hud. This will, of course, be changed
later. The old and new HUD code don't match exactly when laid one over the
other yet, and the new HUD's tapes don't work.