Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Replace ERROR() macro with inline function. In-tree gcc cannot tolerate
the construct like printf("%\s", NULL) resulting from macroexpand of
ERROR(u, NULL), making it impossible to use LIBUFS_DEBUGGING.

With inline function, compiler cannot detect the NULL argument to
known function and does not try to convert it into puts().

In collaboration with: pho

- Merge soft-updates journaling from projects/suj/head into head. This
brings in support for an optional intent log which eliminates the need
for background fsck on unclean shutdown.

Sponsored by: iXsystems, Yahoo!, and Juniper.
With help from: McKusick and Peter Holm

Add a berase() function which uses ioctl(DIOCGDELETE) to erase a slab
of the disk.

Implement cgwrite1(3) function which stored a given cylinder group on disk.

Sponsored by: home.pl

Remove ufs_disk_ctor and ufs_disk_dtor, they never came to fruition. I do
not know of any software using them, and there is no "published API" for
libufs, as it were.

API for opening (and tracking) writable file descriptors per disk.

API to fillout a blank disk. For e.g. newfs.

Store not only the current cylinder group in the series (i.e. next that needs
to be read in) but also the last cylinder group in the series (i.e. what is
stored in the structure).

Add facility to read one, or a string of, cylinger groups.

Hunt for a disk to operate on, if we're passed a partition mountpoint, etc.

Concept reviewed by: phk

Fix typo.

Nuke dumb error reporting code, people can just use disk::d_error. Unify the
DEBUG and d_error initialisation into an ERROR macro, which can both trace and
set the d_error field. Much a more meaningful thing, I should say.

Add the concept of a per-disk error string, and a function which prints it
along with the errno, if one is set.

Wrap the header to prevent multiple inclusion, and mark the DECLS section.

Reminded by: Rachel Hestilow <hestilow@ximian.com>

Add libufs, a library for dealing with UFS filesystems from userland to
the build. It is here to compartmentalise functionality currently duplicated
in many notable programs in the base system. It currently handles block
reads and writes, as well as reading and writing of the filesystem superblock,
and the reading/lookup of inode data. It supports both UFS and UFS2. I
will be maintaining it, and porting programs to use it, however for now, it
is simply being built as part of world.