Fix joystick movement being framerate-dependent

[Macil]

This fixes a bug that when host_maxfps > 72, movement joystick sensitivity would effectively raise proportionally with the framerate. Pushing the stick halfway would make you walk at 72 fps but make you run at maximum speed at 180 fps, etc.

This is because the joystick movement would be summed together over multiple client frames. Only mouse-based movement should be summed together over multiple frames. For joystick-based movement, only the most recent values should be used.

[sezero]

Is this needed in mainstream qs? (if it is, send me a patch.)

[Macil]

It won't be needed there. This is specific to QSS (and well vkQuake) because of a bug in the way it splits the rendering framerate to be separate from the game framerate.