Sync opam file with opam repository

- add missing opam-version field;
- normalise the opam file.

extlib.opam

@@ -1,10 +1,17 @@
 opam-version: "2.0"
+name: "extlib"
+version: "1.8.0"
+synopsis: "A complete yet small extension for OCaml standard library"
+description: """\
+The purpose of this library is to add new functions to OCaml standard library
+modules, to modify some functions in order to get better performances or
+safety (tail-recursive) and also to provide new modules which should be useful
+for day to day programming.
+
+Current goal is to maintain compatibility, new software is encouraged to not use extlib since stdlib
+is now seeing many additions and improvements which make many parts of extlib obsolete.
+For tail-recursion safety consider using other libraries e.g. containers."""
 maintainer: "[email protected]"
-homepage: "https://github.com/ygrek/ocaml-extlib"
-dev-repo: "git+https://github.com/ygrek/ocaml-extlib.git"
-bug-reports: "https://github.com/ygrek/ocaml-extlib/issues"
-doc: ["https://ygrek.org/p/extlib/doc/"]
-license: "LGPL-2.1-only WITH OCaml-LGPL-linking-exception"
 authors: [
   "Nicolas Cannasse"
   "Brian Hurt"
@@ -19,24 +26,17 @@ authors: [
   "Gabriel Scherer"
   "Pietro Abate"
 ]
+license: "LGPL-2.1-only WITH OCaml-LGPL-linking-exception"
+homepage: "https://github.com/ygrek/ocaml-extlib"
+doc: "https://ygrek.org/p/extlib/doc/"
+bug-reports: "https://github.com/ygrek/ocaml-extlib/issues"
 depends: [
   "dune" {>= "1.0"}
   "ocaml" {>= "4.02"}
   "cppo" {build & >= "1.0.1"}
 ]
-synopsis:
-  "A complete yet small extension for OCaml standard library"
-description: """
-The purpose of this library is to add new functions to OCaml standard library
-modules, to modify some functions in order to get better performances or
-safety (tail-recursive) and also to provide new modules which should be useful
-for day to day programming.
-
-Current goal is to maintain compatibility, new software is encouraged to not use extlib since stdlib
-is now seeing many additions and improvements which make many parts of extlib obsolete.
-For tail-recursion safety consider using other libraries e.g. containers.
-"""
 build: [
   ["dune" "build" "-p" name "-j" jobs]
   ["dune" "runtest" "-p" name "-j" jobs] {with-test}
 ]
+dev-repo: "git+https://github.com/ygrek/ocaml-extlib.git"