* cached_block::parent_data can be NULL in a sub transaction in case the
block wasn't part of the parent transaction (but not in low memory
situations). cache_abort_sub_transaction() and cache_detach_sub_transaction()
didn't account for this, though, ie. the block data could end up
corrupted.
* Renamed cached_block::original in original_data.
* Renamed cached_block::data in current_data.
* Added some comments.
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@16108 a95241bf-73f2-0310-859d-f6bbb57e9c96