* gc.c (heap_get_freeobj): improve hot path performance.
* gc.c (heap_get_freeobj_from_next_freepage): replace with
  heap_get_freepage(). It returns freeobj instead of freepage.
  This is not on hot path.



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@44287 b2dd03c8-39d4-4d8f-98ff-823fe69b080e