This reverts commit 5a1dfb04 (r63451)

And mark the functions as async-signal-safe while we're at it to
prevent future developers from making the same mistake as I did :x

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@65316 b2dd03c8-39d4-4d8f-98ff-823fe69b080e