* backport r39276 from trunk. [ruby-dev:46997] [Bug #7825]

* 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/branches/ruby_2_0_0@39279 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* 2013-02-16

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_0_0@39280 b2dd03c8-39d4-4d8f-98ff-823fe69b080e