xfs: update #2 for v3.12-rc1

Here we have defrag support for v5 superblock, a number of bugfixes and
a cleanup or two.

- defrag support for CRC filesystems
- fix endian worning in xlog_recover_get_buf_lsn
- fixes for sparse warnings
- fix for assert in xfs_dir3_leaf_hdr_from_disk
- fix for log recovery of remote symlinks
- fix for log recovery of btree root splits
- fixes formemory allocation failures with ACLs
- fix for assert in xfs_buf_item_relse
- fix for assert in xfs_inode_buf_verify
- fix an assignment in an assert that should be a test in
  xfs_bmbt_change_owner
- remove dead code in xlog_recover_inode_pass2