re2c: 2.2 -> 3.0

https://re2c.org/releases/changelog/changelog.html

While at it added trivial updater script.

pkgs/development/tools/parsing/re2c/default.nix

@@ -2,18 +2,19 @@
 , stdenv
 , fetchFromGitHub
 , autoreconfHook
+, nix-update-script
 , python3
 }:
 
 stdenv.mkDerivation rec {
   pname = "re2c";
-  version = "2.2";
+  version = "3.0";
 
   src = fetchFromGitHub {
     owner  = "skvadrik";
     repo   = "re2c";
     rev    = version;
-    sha256 = "0snfxk1cf2f4dy4hcxd1fx1grav3di0qjgqqn97k85zsf9f6ys78";
+    sha256 = "sha256-ovwmltu97fzNQT0oZHefrAo4yV9HV1NwcY4PTSM5Bro=";
   };
 
   nativeBuildInputs = [
@@ -28,6 +29,12 @@ stdenv.mkDerivation rec {
     patchShebangs run_tests.py
   '';
 
+  passthru = {
+    updateScript = nix-update-script {
+      attrPath = pname;
+    };
+  };
+
   meta = with lib; {
     description = "Tool for writing very fast and very flexible scanners";
     homepage    = "https://re2c.org";