Commit 0df57f5b0f changed markers' movement type from MT_NONE to
MT_SPINNING, since retail code assigned a spin rate, suggesting markers
were meant to spin. However, in some anarchy games, markers are used as
player-positioned cameras. Spinning the cameras makes them hard to use.
Resolve this by preventing markers from spinning in such games.
Fixes: 0df57f5b0f ("Fix retail bug that prevented marker spinning")
Reported-by: flpduarte <https://github.com/dxx-rebirth/dxx-rebirth/issues/456>