modify #untrap prompting further

modify #untrap prompting further

> The intention is, I believe, to cater for the situation where you, a
> chest, and a dungeon-trap are all on the same square; previously
> (C340-71), you wouldn't have been able to check the chest for traps
> because an #untrap in direction '.' would always have tried to disarm
> the dungeon trap. However, since you can't trap-check containers on
> adjacent squares, it'd wouldn't hurt if the question was dispensed
> with when you specify a direction that isn't your square.
>
> (Note that "you cannot deal with traps while trapped!", so there's
> still several situations when you can't trap-check a chest on a
> trap-square, even though you can loot it, until you've untrapped
> yourself; is this really consistent? Should the if(u.utrap) check
> be moved to the "case y:" branch of the switch?)