initialize rest of struct lfs by hand.
(this shouldn't cause a real problem since if superblock is valid,
LFS_SBPAD-sizeof(struct dlfs) bytes after it is always zero-filled, though)
PR/22123 (Izumi Tsutsui)
64 bit block pointers, extended attribute storage, and a few
other things.
This commit does not yet include the code to manipulate the extended
storage (for e.g. ACLs), this will be done later.
Originally written by Kirk McKusick and Network Associates Laboratories for
FreeBSD.
