add ligo_string in simple_utils

vendors/ligo-utils/simple-utils/simple_utils.ml

@@ -14,4 +14,4 @@ module Tree = Tree
 module Region = Region
 module Pos = Pos
 module Var = Var
-
+module Ligo_string = X_string

vendors/ligo-utils/simple-utils/x_string.ml

@@ -0,0 +1,11 @@
+type t =
+  Standard of string
+| Verbatim of string
+
+let pp ppf = function
+    Standard s -> Format.fprintf ppf "%S" s
+  | Verbatim v -> Format.fprintf ppf "{|%s|}" v
+
+let extract = function
+    Standard s -> s
+  | Verbatim v -> v

vendors/ligo-utils/simple-utils/x_string.mli

@@ -0,0 +1,11 @@
+(*
+Ligo_string represent string as they are writen in a ligo program,
+delimited either with double quotes (standard) or with `{|...|}` (Varbatim)
+*)
+
+type t =
+  Standard of string
+| Verbatim of string
+
+val pp : Format.formatter -> t -> unit
+val extract : t -> string