update opam file format to 2.0

opam

@@ -1,18 +1,25 @@
-opam-version: "1.2"
+opam-version: "2.0"
 name: "haxe"
 version: "4.0.0"
+synopsis: "Multi-target universal programming language"
+description: """
+Haxe is an open source toolkit based on a modern,
+high level, static-typed programming language, a cross-compiler,
+a complete cross-platform standard library and ways to access each
+platform's native capabilities."""
 maintainer: ["Haxe Foundation <[email protected]>" "Andy Li <[email protected]>"]
-author: "Haxe Foundation <[email protected]>"
+authors: "Haxe Foundation <[email protected]>"
 homepage: "https://haxe.org/"
 bug-reports: "https://github.com/HaxeFoundation/haxe/issues"
 license: ["GPL2+" "MIT"]
-dev-repo: "https://github.com/HaxeFoundation/haxe.git"
+dev-repo: "git+https://github.com/HaxeFoundation/haxe.git"
 build: [
   [make]
 ]
 install: [make "install" "INSTALL_DIR=%{prefix}%"]
 remove: [make "uninstall" "INSTALL_DIR=%{prefix}%"]
 depends: [
+  "ocaml"               {>= "4.02"}
   "ocamlfind"           {build}
   "camlp4"              {build}
   "sedlex"              {build & <= "1.99.4"} #https://github.com/HaxeFoundation/haxe/issues/7958
@@ -24,5 +31,4 @@ depends: [
   "conf-libpcre"
   "conf-zlib"
   "conf-neko"
-]
-available: [ ocaml-version > "4.02" ]
+]