HAMMER 56F/Many: Stabilization pass

HAMMER 56F/Many: Stabilization pass

* When data is reblocked any related direct-io offsets cached in front-end
  buffer cache buffers must be cleaned out.  This also requires running
  through any snapshotted inodes referencing the same object.

* The flusher must check that the cached B-Tree node has not been flagged
  as deleted (HAMMER_NODE_DELETED) before seeking to it.

* hammer_io_direct_read() now requires and asserts that the second-level
  cached offset in the BIO is a zone-2 offset.

* hammer_io_direct_write() no longer overwrites the second-level cached
  offset with the third level raw disk offset.  It pushes a third level
  to set the raw disk offset.

* When creating a directory entry, set the localization field for pseudo-fs
  support (which isn't quite working yet anyway so no biggy).

* Move the Red-Black tree generator for inodes from hammer_ondisk.c to
  hammer_inode.c.