tests: add get_alloced_bytes function

tests/memtest/libmem.c

@@ -402,3 +402,13 @@ libmem_clear_flags(void* obj, int flags)
   self->flags &= ~flags;
   return 0;
 }
+
+/*****************************************************************************/
+int
+libmem_get_alloced_bytes(void* obj)
+{
+  struct mem_info* self;
+
+  self = (struct mem_info*)obj;
+  return self->total_bytes;
+}

tests/memtest/libmem.h

@@ -14,5 +14,7 @@ int
 libmem_set_flags(void* obj, int flags);
 int
 libmem_clear_flags(void* obj, int flags);
+int
+libmem_get_alloced_bytes(void* obj);
 
 #endif