is not required to split. It was useful to avoid whole process
blocking in Ruby 1.8 but not useful since write() is invoked without
GVL.
(FMODE_WSPLIT_INITIALIZED): Ditto.
* io.c (wsplit_p): Removed.
(io_writable_length): Removed.
(rb_fcntl): Don't update the removed flags.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48476 b2dd03c8-39d4-4d8f-98ff-823fe69b080e