Comment out some dead code.

src/KitTrivial.ml

@@ -9,6 +9,8 @@ class ['self] iter = object (_ : 'self)
   method private visit_'fn _env _x = ()
 end
 
+(* The following are presently unused:
+
 class ['self] map = object (_ : 'self)
   method private extend x env = x, env
   method private visit_'fn _env x = x
@@ -20,3 +22,5 @@ class virtual ['self] reduce = object (self : 'self)
   method private restrict _x z = z
   method private visit_'fn _env _x = self#zero
 end
+
+ *)