Updated opam file.

opam

-opam-version: "1.2"
+opam-version: "2.0"
 maintainer: "francois.pottier@inria.fr"
 authors: [
   "François Pottier <francois.pottier@inria.fr>"
   "Yann Régis-Gianas <yrg@pps.univ-paris-diderot.fr>"
 ]
 homepage: "http://gallium.inria.fr/~fpottier/menhir/"
-dev-repo: "https://gitlab.inria.fr/fpottier/menhir.git"
+dev-repo: "git+https://gitlab.inria.fr/fpottier/menhir.git"
 bug-reports: "menhir@inria.fr"
 build: [
   [make "-f" "Makefile" "PREFIX=%{prefix}%" "USE_OCAMLFIND=true" "docdir=%{doc}%/menhir" "libdir=%{lib}%/menhir" "mandir=%{man}%/man1"]
@@ -17,7 +17,12 @@ remove: [
   [make "-f" "Makefile" "uninstall" "PREFIX=%{prefix}%" "docdir=%{doc}%/menhir" "libdir=%{lib}%/menhir" "mandir=%{man}%/man1"]
 ]
 depends: [
+  "ocaml" {>= "4.02"}
   "ocamlfind" {build}
   "ocamlbuild" {build}
 ]
-available: [ ocaml-version >= "4.02" ]
+synopsis: "LR(1) parser generator"
+url {
+  src: "http://gallium.inria.fr/~fpottier/menhir/menhir-20181005.tar.gz"
+  checksum: "md5=14f46d918cf8571dd735cc22c4fc4811"
+}