dib: Move 'isdigit' utility function to common code.

No change, just simple refactoring.

dib/utils.ml

@@ -76,9 +76,6 @@ let digit_prefix_compare a b =
   let split_prefix str =
     let len = String.length str in
     let digits =
-      let isdigit = function
-        | '0'..'9' -> true
-        | _ -> false in
       try string_index_fn (fun x -> not (isdigit x)) str
       with Not_found -> len in
     match digits with

mllib/common_utils.ml

@@ -58,6 +58,10 @@ let le32_of_int i =
   String.unsafe_set s 3 (Char.unsafe_chr (Int64.to_int c3));
   s
 
+let isdigit = function
+  | '0'..'9' -> true
+  | _ -> false
+
 type wrap_break_t = WrapEOS | WrapSpace | WrapNL
 
 let rec wrap ?(chan = stdout) ?(indent = 0) str =

mllib/common_utils.mli

@@ -32,6 +32,8 @@ val div_roundup64 : int64 -> int64 -> int64
 val int_of_le32 : string -> int64
 val le32_of_int : int64 -> string
 
+val isdigit : char -> bool
+
 val wrap : ?chan:out_channel -> ?indent:int -> string -> unit
 (** Wrap text. *)