NoDrop NPC spawn fix (#1494) * NoDrop NPC spawn fix - Add NoDrop to multiple NPCs to fix them spawning below platforms/displacements. This is best shown spawning a rollermine or combine camera on this platform in gm_construct:  DropToFloor's trace starts in the platform and does not hit the displacement below, so it will drop the NPC to the floor underneath the map. The NPCs chosen for this parameter do not rely on starting on the ground and can be spawned anywhere. - Fixed NoDrop not applying to duped NPCs. - Changed some raw numbers to SF_ enums. * NoDrop duplicator fix