* ext/readline/readline.c: Include ruby/thread.h for
  rb_thread_call_without_gvl2.
  (readline_rl_instream, readline_rl_outstream): Record FILE
  structures allocated by this extension.
  (getc_body): New function extracted from readline_getc.
  (getc_func): New function.
  (readline_getc): Use rb_thread_call_without_gvl2 to invoke getc_func.
  [ruby-dev:47033] [Bug #8749]
  (clear_rl_instream, clear_rl_outstream): Close FILE structure
  allocated by this extention reliably.  [ruby-core:57951] [Bug #9040]
  (readline_readline): Use clear_rl_instream and clear_rl_outstream.
  (readline_s_set_input): Set readline_rl_instream.
  (readline_s_set_output): Set readline_rl_outstream.
  (Init_readline): Don't call readline_s_set_input because
  readline_getc doesn't block other threads for any FILE structure now.

  [ruby-dev:47033] [Bug #8749] reported by Nobuhiro IMAI.
  [ruby-core:57951] [Bug #9040] reporeted by Eamonn Webster.



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43439 b2dd03c8-39d4-4d8f-98ff-823fe69b080e