libxfs: share kernel's xfs_trans_inode.c

libxfs: share kernel's xfs_trans_inode.c

Now that the majority of cosmetic changes and compat shims
are in place, we can directly share kernelspace's
xfs_trans_inode.c with just a couple more small tweaks.
In addition to the file move,

* ili_fsync_fields is added to xfs_inode_log_item (but not used)
* test_and_set_bit() helper is created

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>