libfrog: emulate deprecated attrlist functionality in libattr

Break our dependence on the (deprecated) libattr by emulating the
necessary pieces in libfrog.  It's a little sketchy to open-code these
symbols, but they're originally from XFS so we trust ourselves.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>