Fix printing for constrained infix operator bindings:
Fix printing for constrained infix operator bindings:

   let (++) : _  = (+)

was previously printed as

   let ++ : _  = (+)

msprotz/ocaml,yunxing/ocaml,eliberis/ocaml,msprotz/ocaml,gerdstolpmann/ocaml,gerdstolpmann/ocaml,eliberis/ocaml,yunxing/ocaml,gerdstolpmann/ocaml,eliberis/ocaml,gerdstolpmann/ocaml,gerdstolpmann/ocaml,eliberis/ocaml,eliberis/ocaml,yunxing/ocaml,msprotz/ocaml,msprotz/ocaml,msprotz/ocaml,yunxing/ocaml,yunxing/ocaml