message: One more assertion in SlabAlloc::do_free()
  This would be one possible source of unaligned refs entering
  the free list.
diff: @@ -602,6 +602,7 @@ void SlabAlloc::do_free(ref_type ref, char* addr) noexcept
  // Free space in read only segment is tracked separately
  try {
  REALM_ASSERT_RELEASE(ref != 0);
  + REALM_ASSERT_RELEASE_EX(!(ref & 7), ref);
  auto next = m_free_read_only.lower_bound(ref);
  if (next != m_free_read_only.end()) {
  REALM_ASSERT_RELEASE_EX(ref + size <= next->first, ref, size, next->first, next->second);
  