mem/pool: improve the scalable memory allocator.

- thread ID is no longer needed.
- Add an embedded option "USE_PAGE".
  With USE_PAGE, allocation becomes page-level.
  Without USE_PAGE, allocation becomes object-level.

Author: shintaro-iwasaki

src/include/queue/zm_queue_types.h

@@ -41,7 +41,7 @@ struct zm_msqnode {
 struct zm_msqueue {
     zm_atomic_ptr_t head ZM_ALLIGN_TO_CACHELINE;
     zm_atomic_ptr_t tail ZM_ALLIGN_TO_CACHELINE;
-    zm_pool_t pool;
+    zm_pool_t pool ZM_ALLIGN_TO_CACHELINE;
 };
 
 /* faqueue */