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/modules/projectiles/ammunition/magnetic.dm

@@ -9,7 +9,7 @@
 	var/remaining = 9
 	preserve_item = 1
 
-/obj/item/magnetic_ammo/examine(mob/user)
+/obj/item/magnetic_ammo/examine(mob/user, distance, infix, suffix)
 	. = ..()
 	. += "There [(remaining == 1)? "is" : "are"] [remaining] flechette\s left!"
 

code/modules/projectiles/ammunition/smartmag.dm

@@ -49,7 +49,7 @@
 			last_production_time = world.time
 			produce()
 
-/obj/item/ammo_magazine/smart/examine(mob/user)
+/obj/item/ammo_magazine/smart/examine(mob/user, distance, infix, suffix)
 	. = ..()
 
 	if(attached_cell)
@@ -223,4 +223,4 @@
 	ammo_type = null
 	production_cost = null
 
-	return
+	return