HAMMER 12/many - add VOPs for symlinks, device, and fifo support.

HAMMER 12/many - add VOPs for symlinks, device, and fifo support.

* Add some missing VOP bits.  Add a fixed attribute record type and store
  the symlink path as fixed attribute record #1.

* Adjust hammer_inode_data to add missing major and minor device fields.

* Add support for adding generic records and special case deletion of
  an object's entire set of records.

* Fix a minor bug that was causing the root cluster to be improperly kfree()'d.