du: Complete libxo transitionHEADmain

* Use xo_warn() / xo_err() instead of warn() / err().

* Add a test case for the POSIX-mandated stdout error check.

* While here, don't assume the size of off_t, address some style issues,
  and broaden the use of bool instead of int.

* Reorder SEE ALSO section.

MFC after:	1 week
Sponsored by:	Klara, Inc.
Reviewed by:	allanjude
Differential Revision:	https://reviews.freebsd.org/D56402

0 files changed, 0 insertions, 0 deletions