Aliasing bat_wings -> demon_wings

Reason: It seems as though demon wings covers the majority of non-angelic or bird-type wings, and bat_wings seems to be used interchangeably with demon_wings. It could be done the other way around if i'm wrong, but I prefer demon_wings.

forum #49560
and
forum #22655

Basically, they are separate enough but there is a lot of crossover, at least that is how I understood it.

At either rate, I don't think it was viewed as interchangeable.

Whoops, I should have searched first.