HAMMER 40A/Many: Inode/link-count sequencer.

HAMMER 40A/Many: Inode/link-count sequencer.

* Remove the hammer_depend structure and build the dependancies directly
  into the hammer_record structure.

* Attempt to implement layout rules to ensure connectivity is maintained.
  This means, for example, that before HAMMER can flush a newly created
  file it will make sure the file has namespace connectivity to the
  directory it was created it, recursively to the root.

NOTE: 40A destabilizes the filesystem a bit, it's going to take a few
passes to get everything working properly.  There are numerous issues
with this commit.