* gc.c: fix rb_objspace_t.
  * make "struct heap" and move most of variables
    in rb_objspace_t::heap.
  * rename rb_objspace_t::heap::sorted to
     rb_objspace_t::heap_sorted_pages
     and make a macro heap_sorted_pages.
  * rename rb_objspace_t::heap::range to
     rb_objspace_t::heap_range and rename macros
     lomem/himem to heap_lomem/heap_himem.



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43360 b2dd03c8-39d4-4d8f-98ff-823fe69b080e