git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_1_8@28861 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
former is provided by ruby's defines.h but the latter is offered
by some systems only by chance. this fixes build failure with VC.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_1_8@28861 b2dd03c8-39d4-4d8f-98ff-823fe69b080e