use lang 2.0 and format dune files (#440)

dune-project

@@ -1,4 +1,5 @@
-(lang dune 1.11)
+(lang dune 2.0)
+(formatting (enabled_for dune))
 (name utop)
 
 (generate_opam_files)

examples/custom-utop/dune

@@ -1,4 +1,5 @@
 (executable
  (name myutop)
+ (modes byte)
  (link_flags -linkall)
  (libraries utop))

examples/interact/dune

@@ -1,4 +1,5 @@
 (executable
  (name test_program)
+ (modes byte)
  (link_flags -linkall)
  (libraries utop))

src/lib/dune

@@ -3,7 +3,8 @@
  (public_name utop)
  (wrapped false)
  (modes byte)
- (libraries compiler-libs.toplevel findlib.top lambda-term logs.lwt threads zed)
+ (libraries compiler-libs.toplevel findlib.top lambda-term logs.lwt threads
+   zed)
  (preprocess
   (action
    (run %{bin:cppo} -V OCAML:%{ocaml_version} %{input-file}))))

utop.opam

@@ -10,7 +10,7 @@ homepage: "https://github.com/ocaml-community/utop"
 doc: "https://ocaml-community.github.io/utop/"
 bug-reports: "https://github.com/ocaml-community/utop/issues"
 depends: [
-  "dune" {>= "1.11"}
+  "dune" {>= "2.0"}
   "ocaml" {>= "4.08.0"}
   "base-unix"
   "base-threads"