Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

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

MFC r239959:

Work around several warnings from clang in the xfs filesystem, when
linking it statically into the kernel. With our gcc in base there are
no warnings, so also remove the WERROR= from the module makefile.

Noted by: Eir Nym <eirnym@gmail.com>

MFC r240011:

Partially revert r239959, after actually fixing most of the clang
warnings in sys/gnu/fs/xfs. The only warnings that still need to be
suppressed are those about array bound overruns of flexible array
members in xfs_dir2_{block,sf}.c, which are too expensive (in terms of
cascading code changes) to fix.

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

Fix the build by using proper format.

Pointy hat: me
Approved by: kib

Switch cmd argument of ioctl to u_long as elsewhere in the kernel.
Propagate this change down the callchain.

Approved by: kan (maintainer)
Approved by: ed (mentor)

Set magic fbsd:nokeywords property that allows files to bypass
keyword expansion. (file-specific replacement for CVSROOT/exclude)

Bow to incomplete GCC 4. constant propagation optimizations and
initialize some of the local variables GCC claims are being used
uninitialized.

Sync XFS for FreeBSD tree with newer changes from SGI XFS for Linux tree.
Improve support for writing to XFS partitions.

Work done by: Russell Cattelan <cattelan at xfs dot org>

Cope with -Wundef. This means including xfs_macros.h early in a few more
files and changing #if XXXKAN -> #ifdef XXXKAN.

# this is just compile tested, since I don't have xfs partitions.

Initial import of read-only support for SGI's XFS filesystem.

Contributed by: XFS for FreeBSD project