examine signature changed to include distance

- 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.

code/game/objects/structures/fence.dm

@@ -27,7 +27,7 @@
 	update_cut_status()
 	return ..()
 
-/obj/structure/fence/examine(mob/user)
+/obj/structure/fence/examine(mob/user, distance, infix, suffix)
 	. = ..()
 
 	switch(hole_size)
@@ -176,4 +176,4 @@
 #undef NO_HOLE
 #undef MEDIUM_HOLE
 #undef LARGE_HOLE
-#undef MAX_HOLE_SIZE
+#undef MAX_HOLE_SIZE