* include/ruby/ruby.h: modify struct RObject and RClass for optimizing
  T_OBJECT space.  [ruby-dev:31853]
  (ROBJECT_LEN, ROBJECT_PTR)
  (RCLASS_IV_TBL, RCLASS_M_TBL, RCLASS_SUPER, RCLASS_IV_INDEX_TBL)
  (RMODULE_IV_TBL, RMODULE_M_TBL, RMODULE_SUPER): abstract accessor
  defined.

* variable.c: support the modified RObject and RClass.

* object.c: ditto.

* class.c: ditto.

* gc.c: ditto.

* marshal.c: ditto.

* eval_method.ci: use the abstract accessor.

* insns.def: ditto.

* proc.c: ditto.

* struct.c: ditto.

* eval.c: ditto.

* error.c: ditto.

* vm.c: ditto.

* insnhelper.ci: ditto.

* ext/digest/digest.c: ditto.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@13543 b2dd03c8-39d4-4d8f-98ff-823fe69b080e