io.c: keep fptr read-closed

* io.c (rb_io_close_read): keep fptr in write_io to be discarded, to
  fix freed pointer access when it is in use by other threads, and get
  rid of potential memory/fd leak.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43112 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* 2013-10-02

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43113 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
io.c: get rid of race condition

* io.c (rb_io_close_write): detach tied IO for writing before closing
  to get rid of race condition.  [ruby-list:49598]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43114 b2dd03c8-39d4-4d8f-98ff-823fe69b080e