* ext/readline/readline.c (Init_readline, readline_s_set_output)
(clear_rl_outstream, readline_s_set_input, clear_rl_instream)
(readline_readline): fix causing SEGV if closed IO object that is
  set Readline.input or Readline.output. Patched by akr
  [ruby-dev:47509] [Bug #8644]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@42402 b2dd03c8-39d4-4d8f-98ff-823fe69b080e