Returns old alien weeds (#4075)

This update returns the alien weeds to their old behavior, instead of just being regular vines that turns any alien round into a giant clusterfuck. Also fixes alien acid being unable to melt the floor.

code/game/objects/effects/aliens.dm

@@ -35,6 +35,11 @@
 		if(istype(target, /turf/simulated/wall)) // I hate turf code.
 			var/turf/simulated/wall/W = target
 			W.dismantle_wall(1)
+
+		if(istype(target, /turf/simulated/floor))
+			var/turf/simulated/floor/F = target
+			F.ChangeTurf(F.baseturf)
+
 		else
 			qdel(target)
 		qdel(src)