Adds flush in Transitioning.Stdlib, and replaces Pervasives.flush in dotgraph.

Avoids a compilation warning with ocaml >= 4.08.

src/libraries/stdlib/transitioning.ml.in

@@ -29,6 +29,7 @@ module Stdlib = struct
   let max = max
   let min_int = min_int
   let max_int = max_int
+  let flush = flush
 end
 
 [@@@ warning "-3"]

src/libraries/stdlib/transitioning.mli

@@ -42,6 +42,7 @@ module Stdlib: sig
   val max: 'a -> 'a -> 'a
   val min_int: int
   val max_int: int
+  val flush: out_channel -> unit
 end
 
 (** 4.08 *)

src/libraries/utils/dotgraph.ml

@@ -128,7 +128,7 @@ let close dot =
     begin
       Format.fprintf dot.fmt "}@." ;
       dot.fmt <- Format.err_formatter ;
-      Pervasives.flush out ; close_out out ;
+      Transitioning.Stdlib.flush out ; close_out out ;
       dot.out <- None ;
     end