ruby/io.h: get rid of conflict on AIX
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39987 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
ruby/io.h: get rid of conflict on AIX
to get rid of conflict on AIX. [ruby-core:53765] [Bug #8174]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39987 b2dd03c8-39d4-4d8f-98ff-823fe69b080e