* class.c, compile.c, eval.c, gc.h, insns.def, internal.h, method.h,
  variable.c, vm.c, vm_core.c, vm_insnhelper.c, vm_insnhelper.h,
  vm_method.c: Implement class hierarchy method cache invalidation.

  [ruby-core:55053] [Feature #8426] [GH-387]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@42822 b2dd03c8-39d4-4d8f-98ff-823fe69b080e