Removed untrue comment in set_sindexes about releasing sindex_block.
Added RSI comment about malperformance of set_sindexes.
Added RSI comment about the get_sindexes function that takes a superblock_t.
Made the real_superblock_t use a precious initializer list.
Split apart outdated from up-to-date parts of comment in process_a_leaf.
Made access_ref_count_ be an intptr_t.