let players walk if their position changes and not if they hold specific keys

let players walk if their position changes and not if they hold specific keys
and disable the animation update globalstep on singleplayer mode because it's not necessary and 3d person view is independent from this globalstep
`v` isn't a good variable name.  I expect something named `v` to be vector, but it's really a number containing the distance moved times 6 divided by dtime used for the animation speed, so `animation_speed` would be a better variable name.