* gc.c: fix layout of rb_objsapce_t to improve cache locality.
  newobj_of() accesses:
  (1) rb_objspace_t::flags
  (2) rb_objspace_t::eden_heap::freelist
  (3) and rb_objspace_t::eden_heap::free_pages if freelist is NULL.



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47468 b2dd03c8-39d4-4d8f-98ff-823fe69b080e