Add padding to malloc increase

Author: jhawthorn

gc/default/default.c

@@ -466,8 +466,8 @@ enum gc_mode {
 
 typedef struct rb_objspace {
     struct {
+        alignas(64) size_t increase;
         size_t limit;
-        size_t increase;
 #if MALLOC_ALLOCATED_SIZE
         size_t allocated_size;
         size_t allocations;
@@ -586,7 +586,7 @@ typedef struct rb_objspace {
         size_t old_objects_limit;
 
 #if RGENGC_ESTIMATE_OLDMALLOC
-        size_t oldmalloc_increase;
+        alignas(64) size_t oldmalloc_increase;
         size_t oldmalloc_increase_limit;
 #endif