* variable.c (rb_const_set): fix WB miss.

  WBs had located before creating reference between a klass
  and constant value. It causes GC bug.

    # pseudo code:
    WB(klass, value); # WB and remember klass
    st_insert(klass->const_table, const_id, value);

  `st_insert()' can cause GC before inserting `value' and
  forget `klass' from the remember set. After that, relationship
  between `klass' and `value' are created with constant table.
  Now, `value' can be young (shady) object and `klass' can be old
  object, without remembering `klass' object.
  At the next GC, old `klass' object will be skipped and
  young (shady) `value' will be miss-collected. -> GC bug

  Lesson: The place of a WB is important.



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@41396 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* 2013-06-19

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@41397 b2dd03c8-39d4-4d8f-98ff-823fe69b080e