ufs2 fails to mount on x86_64, claiming bad magic.  This is because
ufs_super_block_third's fs_un1 member is padded out by 4 bytes for 8-byte
alignment, pushing down the rest of the struct.

Forcing this to be packed solves it.  I took a quick look over other
on-disk structures and didn't immediately find other problems.  I was able
to mount & ls a populated ufs2 filesystem w/ this change.
Signed-off-by: NEric Sandeen <sandeen@redhat.com>
Cc: Evgeniy Dushistov <dushistov@mail.ru>
Cc: <stable@kernel.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>