MFC: r284589

MFC: r284589
  Add the ability to detect ZFS and GELI encrypted file systems to fstyp(8)

MFC: r284644
  Fix GCC Warnings

MFC: r284728
  Only build ZFS support in absense of WITHOUT_ZFS

MFC: r285426
  Remove excess copyrights

MFC: r286569
  Use GELI sentinel constant

MFC: r287937
  Eliminate unneeded copying of vdev data, goto, etc. and add a note
  that checksum of vdev label should be checked (which is not done
  currently).

  No functional change.

  While I'm there, raise WARNS to 2.

MFC: r292757
  Fix order of includes in usr.sbin/fstyp/zfs.c

MFC: r292829
  Eliminate unneeded includes.

git-svn-id: svn://svn.freebsd.org/base/stable/10@293776 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f