* class.c (rb_include_class_new), eval.c (rb_using_refinement):
  make classes/modules (who share method table) shady.
  If module `a' and `b' shares method table m_tbl and new method
  with iseq is added, then write barrier is applied only `a' or `b'.
  To avoid this issue, shade such classes/modules.
* vm_method.c (rb_method_entry_make): add write barriers.



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@41580 b2dd03c8-39d4-4d8f-98ff-823fe69b080e