- distance is INFINITE, 0, or a positive integer based on get_dist() between
the examiner and examinee's turfs when they are on the same Z. When the
examiner is dead or a ghost, distance is always 0.
- also updates /examine( implementations to use it!
- adds w_class_to_name proc for reusing "It is a X item." examine behavior.
NB. In some cases we go from a more complex image() to a single icon_state string and I assume this works for every case but do not care to check because of the sheer scale of extra fiddly effort. Buyer beware, not my code.