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

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

The last big commit: let usr.sbin/ use WARNS=6 by default.

style.Makefile(5)

Make extattrctl WARNS?=2-safe:
o remove extraneous extern's
o prototype functions
o combine multiple return (0)'s into a single return (0) at the
end of main()

Approved by: rwatson
Obtained from: TrustedBSD Project

o Reflect moving of extattr_namespace calls to libc from libutil; no
longer need to link libutil into command-line extended attribute
utilities.

Obtained from: TrustedBSD Project

Perform a major cleanup of the usr.sbin Makefiles.
These are not perfectly in agreement with each other style-wise, but they
are orders of orders of magnitude more consistent style-wise than before.

Remove GCC'isms in CFLAGS.

Fix LDADD and add missing DPADD.

- Backout botched attempt to introduce MANSECT feature.
- MAN[1-9] -> MAN.

Set the default manual section for usr.sbin/ to 8.

o Update extattrctl to take into account the updated EA interface with
explicit namespaces. Modify it to use libutil for string/constant
namespace conversions. Update the documentation to take into account
the new interface.

Obtained from: TrustedBSD Project

Introduced /usr/sbin/extattrctl, a utility for managing UFS/FFS extended
attributes (recently committed). Using extattrctl, the extended attribute
service may be started and stopped for specific file systems; specific
attributes may be enabled or disabled, and the backing file for each
attribute configured. Also, backing files may be initialized.

Reviewed by: adrian, bp, freebsd-fs, the unthanked masses
Obtained from: TrustedBSD