* vm_trace.c: add new method TracePoint.stat to debug
  TracePoint mechanism.
  Ruby users should not use this method. So I don't note this method
  in the NEWS file.
* test/runner.rb: detect zombie active TracePoints with
  TracePoint.stat.



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@46420 b2dd03c8-39d4-4d8f-98ff-823fe69b080e