some infix operators when applied to arguments pretty print incorrectly

[alleystoughton]

op (++) : int -> int -> int.

op x = 3 ++ 5.

print x.
(*
* In [operators, predicates or exceptions]:

op x : int = ++ 3 5.
*)

op (::) : int -> int -> int.

op y = 3 :: 5.

print y.
(*
* In [operators, predicates or exceptions]:

op y : int = 3 :: 5.
*)

op (--) : int -> int -> int.

op z = 3 -- 5.

print z.
(*
* In [operators, predicates or exceptions]:

op z : int = -- 3 5.
*)