Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

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

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

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

- 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

Correct an apparent typo.

PR: bin/53515
Submitted by: Lukas Ertl <l.ertl@univie.ac.at>
Approved by: jmallett

Reduce diffs with code in Perforce:
Parenthesise return values.

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.

Fill out (zero) and fill in (when doing getino()) the minimum and maximum
inodes in our inoblock (disk->d_ino{min,max}) appropriately.

In getino, have our DEBUG message in the unhandled case mention that it
does not know what sort of UFS filesystem this is.

Add some DEBUG(NULL)'s to function entry points.

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.