- Add documentation on how to use the MD driver to be able to use NTFS
stripe and volume sets in Linux and generally cleanup documentation
a bit.

Remove all uses of kdev_t in favour of struct block_device *:
- Change compress.c::ntfs_file_read_compressed_block() to use sb_getblk()
instead of getblk().
- Change super.c::ntfs_fill_suoer() to use bdev_hardsect_size() instead
of get_hardsect_size().
- No need to get old blocksize in super.c::ntfs_fill_super() as
fs/super.c::get_sb_bdev() already does this.
- Set bh->b_bdev instead of bh->b_dev throughout aops.c.