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

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

The -r option can also cause the files to be extended (not
necessarily truncated).

Markup fixes.

Allow to specify size in terabytes by using T or t suffix.
This speeds up my testing a bit. Because truncate(1) doesn't allocate
blocks on file system before they are used, it is very useful to
emulate huge file systems:

# truncate -s 16T fs.img
# mdconfig -a -f fs.img
# newfs /dev/mdX

(-t swap can be used as well)

Added the EXIT STATUS section where appropriate.

Make size suffix case insensitive.

PR: bin/27604
Submitted by: David Xu <davidx@viasoft.com.cn>

* Update author's e-mail address.

* When the author of an utility also wrote its manual page (a rarety, I
know), it is not necessary to say that the utility "and this manual
page" were written by the author.

Use the .Cm macro to mark up the modifiers of the -s flag's size argument.

mdoc(7) police: utilize the new .Ex macro.

Remove whitespace at EOL.

mdoc(7) police: use canonical form of .Dd macro.

mdoc(7) police: use the new features of the Nm macro.

Merge the truncate(1) utility onto the RELENG_4 branch and adjust
the HISTORY section to reflect the first release of FreeBSD in
which this utility will appear.

truncate.c:
Do not include unused header files.
Add rcsid.
Change copyright.

truncate.1:
Add AUTHORS section.

Submitted by: charnier

Add a STANDARDS section to discourage the use of this utility
in environments where portability is a concern.

Import the new truncate(1) utility.

Approved by: jdp