fix U382 - missing map display update

fix U382 - missing map display update

> Receiving Excalibur from a fountain while blind doesn't update the
> display (i.e. the missing fountain) immediately.

     Various other topology changes had the same problem.  The display
was only being updated if the hero was invisible on the assumption that
it wouldn't matter otherwise, but a blind character who moved off the
affected location would still have the old map info (fountain, trap, &c)
shown--until he walked back onto that spot or searched next to it or
regained sight--even though the player is told about the map change as
it happens.