configure.in: get rid of macro redefinition
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@53263 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
configure.in: get rid of macro redefinition
to suppress warnings by gcc5.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@53263 b2dd03c8-39d4-4d8f-98ff-823fe69b080e