[persistent-data, dm-array] change variables named block_size to sizeof_of_block for agk.
[persistent-data, dm-array] Use an explicit cast when formatting error messages.
[persistent-data, dm-array] whitespace
[persistent-data, dm-array] remove some duplicate calculation of max_entries per array block.
[persistent-data, dm-array] refactor grow()
[persistent-data, dm-array] Improve a couple of error messages.