vm_call_cfunc() instead of klass. * vm.c (rb_thread_method_id_and_klass): traverse parent_iseq. * thread.c (call_trace_proc): use rb_thread_method_id_and_klass(). git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@13877 b2dd03c8-39d4-4d8f-98ff-823fe69b080e