* gc.c (gc_stat): add internal information.
  * heap_swept_slot
  * malloc_increase
  * malloc_limit
  * remembered_shady_object
  * remembered_shady_object_limit
  * old_object
  * old_object_limit
  * oldmalloc_increase
  * oldmalloc_limit
* gc.c (gc_stat): rename names.
  * heap_live_num -> heap_live_slot
  * heap_free_num -> heap_free_slot
  * heap_final_slot -> heap_final_slot
  Quote from RDoc of GC.stat():
    "The contents of the hash are implementation specific and may
    be changed in the future."
* test/ruby/test_gc.rb: catch up this change.



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43835 b2dd03c8-39d4-4d8f-98ff-823fe69b080e