- Add check at mount time to verify that the number of inodes on the
  volume does not exceed 2^32 - 1, which is the maximum allowed for
  NTFS according to Microsoft.
- Change mft_no member of ntfs_inode structure to be unsigned long.
  Update all users. This makes ntfs_inode->mft_no just a copy of struct
  inode->i_ino. But we can't just always use struct inode->i_ino and
  remove mft_no because extent inodes do not have an attached struct
  inode.