Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Fix a small typo nit

Removed "tail +5" from the command used to sanity check changes to
mtree files -- the 5-line header is no longer printed when mtree(8)
is run with -n (as of mtree/create.c,v 1.34).

Approved by: re (kensmith)

Sigh, this README is not a shell script.

Remind developers to update hier(7) if they make changes to these files.

Fix a small typo

Add missing -p /tmp/MTREE to mtree command in README so that it
will actually work now.

Remove tabs and once again sort the *.dist files.

$Id$ -> $FreeBSD$

Fix script in README to actually work, empty lines produce as
much a diff as lines with the wrong stuff on it.

Add references in mtree data files to the README.

An explination of how to keep these files in good working order.

Reviewed by: bde