bm_vm_thread_*. suggested by ko1.
* benchmark/bm_vm4_pipe.rb: ditto.
* benchmark/bm_vm4_alive_check1.rb: ditto.
* benchmark/bm_vm4_pass_flood.rb: ditto.



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@32094 b2dd03c8-39d4-4d8f-98ff-823fe69b080e