Duke3D: Preserve STAT_ACTOR/MISC actors with xrepeat==0 while using pre-v1.4 CON code.

At least in STAT_ACTOR's case, this fixed assault captains being removed upon becoming invisible while using v1.3d's CON code.

I tried looking for relevant use-cases involving STAT_MISC, albeit it seems to be commonly used for actors whose repeat values are changed to 0. I'm also not sure if the viewscreens should be given the same treatment in G_MoveStandables.

Either way, this should have no impact with CON files made for v1.4-1.5.