Import digest v3.1.0 from ruby/digest

ext/digest/digest.gemspec

@@ -1,12 +1,12 @@
 # coding: utf-8
 # frozen_string_literal: true
 
-version_module = Module.new do
+Gem::Specification.new do |spec|
+  version_module = Module.new do
     version_rb = File.join(__dir__, "lib/digest/version.rb")
     module_eval(File.read(version_rb), version_rb)
-end
+  end
 
-Gem::Specification.new do |spec|
   spec.name          = "digest"
   spec.version       = version_module::Digest::VERSION
   spec.authors       = ["Akinori MUSHA"]

ext/digest/install_headers.rb

@@ -1,13 +0,0 @@
-require "fileutils"
-
-*files, dest = ARGV
-
-if File.exist?(File.join(dest, "ruby.h"))
-  warn "installing header files"
-
-  files.each { |file|
-    FileUtils.install file, dest, mode: 0644, verbose: true
-  }
-else
-  warn "not installing header files when installed as an external library"
-end

ext/digest/lib/digest/version.rb

@@ -1,5 +1,5 @@
 # frozen_string_literal: true
 
 module Digest
-  VERSION = "3.1.0.pre3"
+  VERSION = "3.1.0"
 end