ruby/io.h: get rid of conflict on AIX
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39993 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
ruby/io.h: get rid of conflict on AIX
longer needed. patch suggested by edelsohn (David Edelsohn) in
[ruby-core:53815]. [Bug #8174]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39993 b2dd03c8-39d4-4d8f-98ff-823fe69b080e