addded support for pack hints - writes related to files that have slow sequential read access
and are written and deleted as a unit. Example: video, mp3 etc.

- assuming we have multiple APs per pool, the last one in each AP is dedicated to packed writes.
- such an ap is associated to an inode number and all writes with a hint relating it an inode
that should be "pack"ed are written sequentially to this ap
- when the ap is full, we disassociate it from the ino, so it can service other inodes if necessary
  TODO: perhaps we can settle for the timeout (see next) and omit this code
- whenever a certain timeout passes (currently 10ms), the AP can be associated to an other inode.
  this helps avoid APs never getting new data, once a packed file is done writing.
Merge branch 'openssd' of https://github.com/MatiasBjorling/linux_openssd into openssd
small fix of merge