cont.c: refined error message
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@63351 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
cont.c: refined error message
failure at setting a guard page.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@63351 b2dd03c8-39d4-4d8f-98ff-823fe69b080e