* gc.c (gc_stat_internal): add compatible layer.
  From Ruby 2.2, keys of GC.stat are changed [Feature #9924].
  To provide compatible layer, GC.stat add a default_proc
  (if default_proc of given Hash object is not set).
  At first use of this compatible layer of interpreter process,
  show a warning message like that:
  program: GC.stat[:total_allocated_object]
  warning message: "warning: GC.stat keys were changed from Ruby
  2.1. In this case,  you refer to obsolete `total_allocated_object'
  (new key is `total_allocated_objects').
  Please check <https://bugs.ruby-lang.org/issues/9924>
  for more information."
  Pleaes correct my English message :)
* hash.c (rb_hash_set_default_proc): export (in internal).
* internal.h: ditto.



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48423 b2dd03c8-39d4-4d8f-98ff-823fe69b080e