* vm.c (rb_thread_mark): mark a working Proc of bmethod
  (a method defined by define_method) even if the method was removed.
  We could not trace working Proc object which represents the body
  of bmethod if the method was removed (alias/undef/overridden).
  Simply, it was mark miss.
  This patch by Kazuki Tsujimoto. [Bug #7825]
  NOTE: We can brush up this marking because we do not need to mark
  `me' on each living control frame. We need to mark `me's
  only if `me' was free'ed. This is future work after Ruby 2.0.0.
* test/ruby/test_method.rb: add a test.



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39276 b2dd03c8-39d4-4d8f-98ff-823fe69b080e