add a debug function.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@58408 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
add a debug function.
for all living threads.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@58408 b2dd03c8-39d4-4d8f-98ff-823fe69b080e