MT#55283 fix alloc alignment

We need at least 64 bits for atomic64

Change-Id: I08724d204f2a1603088c8737ca096a4b64314f6b
(cherry picked from commit 649e225bc9)
(cherry picked from commit b980166dba)

lib/bufferpool.h

@@ -3,7 +3,7 @@
 
 #include "obj.h"
 
-#define BUFFERPOOL_ALIGNMENT (sizeof(void *)) // bytes
+#define BUFFERPOOL_ALIGNMENT (MAX(sizeof(void *), 8)) // bytes
 #define BUFFERPOOL_ALIGN(x) (((x + BUFFERPOOL_ALIGNMENT - 1) / BUFFERPOOL_ALIGNMENT) * BUFFERPOOL_ALIGNMENT)
 
 #define BUFFERPOOL_SHARD_SIZE ((size_t) (1LL<<24)) // 16 MB, must be a power of two