Altitude lock input for Halo 3's Hornet

I always liked the altitude lock feature on Reach's Falcon so I threw together a tertiary weapon that does the same thing for the Halo 3 Hornet. Tag release contains both the standard and lite Hornet tags as well as an updated hud_messages.txt for the input instruction.

Altitude lock is toggled via the melee input. There is also a sound effect that plays when you toggle it for extra feedback.

I fixed a bug I overlooked where exiting the vehicle while altitude lock is engaged will cause the Hornet to be dragged away. A counter force will now be applied to counteract this when the vehicle is exited.