Avoid common symbols for fsck_lfs.

Remove a dead data structure.

Add 64-bit directory entry structures, and adjust accessors accordingly.

The LFS64 directory entry has a 64-bit inode number. This is stored as
two 32-bit values to avoid inducing 64-bit alignment requirements.

The exposed type for manipulating directory entries is now
LFS_DIRHEADER, following the same convention as e.g. IFILE and SEGUSE.
(But with LFS_ on it, because.)

Pass around struct lfs_dirheader instead of struct lfs_direct.

Hack up dinode usage to be 64 vs. 32 as needed. Part 1.

(This part changes the native lfs code; the ufs-derived code already
has 64 vs. 32 logic, but as aspects of it are unsafe, and don't
entirely interoperate cleanly with the lfs 64/32 stuff, pass 2 will be
rehashing that.)

struct direct -> struct lfs_direct
struct dirtemplate -> struct lfs_dirtemplate
struct odirtemplate -> struct lfs_odirtemplate
DT_* -> LFS_DT_*

ufs -> ulfs for fsck_lfs.

branches: 1.9.2; 1.9.8;
share more code.

branches: 1.8.42;
constify

remove a prototype of a non-exist function.

use bounded string op

Add support for UFS2. UFS2 is an enhanced FFS, adding support for
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.

Add working writing ability to fsck_lfs, including roll-forward, based on
a partial-segment writer ported from the kernel.

Convert to NetBSD source code style

RCS Id police.

Initial checkin of fsck_lfs. This version cannot do any repair (-p flag
does nothing, and one of -p or -n is required) but can be useful as a
diagnostic tool.