merge revision(s) 57415,57463,57474:

    eval.c: copy special exception

    * eval.c (setup_exception): make unfrozen copy of special
      exception before setting up a cause.
    reduce iterations for slower machines
    test_io.rb: separate a test

    * test/ruby/test_io.rb (test_closed_stream_in_rescue): run in a
      separated process.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_4@57939 b2dd03c8-39d4-4d8f-98ff-823fe69b080e