Fix test failure of binmode from r40879

http://ruby-mswin.cloudapp.net/vc10-x64/ruby-trunk/log/20130521T131601Z.log.html.gz

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@40892 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

test/digest/test_digest.rb

@@ -80,7 +80,7 @@ module TestDigest
   end
 
   def test_s_file
-    Tempfile.create("test_digest_file") { |tmpfile|
+    Tempfile.create("test_digest_file", mode: File::BINARY) { |tmpfile|
       str = "hello, world.\r\n"
       tmpfile.print str
       tmpfile.close