- Copy stable/10 (r259064) to releng/10.0 as part of the
10.0-RELEASE cycle.
- Update __FreeBSD_version [1]
- Set branch name to -RC1

[1] 10.0-CURRENT __FreeBSD_version value ended at '55', so
start releng/10.0 at '100' so the branch is started with
a value ending in zero.

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

- Print the nmount(2) provided error message only when it is set.
- Ensure that the error message is NUL-terminated before printing it.

PR: bin/147482
MFC after: 2 weeks

Initialize iov and iovlen before use.

Reported by: Lucius Windschuh <lwindschuh@googlemail.com>

- Move from mount(2) to nmount(2). This should allow to convert MNT_SNAPSHOT
flag from a mount flag to FS-specific flag.
- Simplify usage. Instead of 'mksnap_ffs /mnt/foo /mnt/foo/snap' allow to
give only one argument: 'mksnap_ffs /mnt/foo/snap'. Old usage is also
accepted for now.
- Add an example of how to mount a snapshot.

Make sure we don't pass garbage to the kernel.

The filesystem is named "ufs" not "ffs".

Style nit in previous commit.

Preserve acls option on mounts when taking a snapshot.

Submitted by: Wiktor Niesiobedzki <freebsd-lists@w.evip.pl>

Check that the user running mksnap_ffs has permission to create and
remove a snapshot file from the directory in which they have requested
to have it made. If they do not have write permission in the directory
or the directory is sticky and not owned by the user, then they
will not be able to remove the snapshot when they are done with it.

style(9): sort functions.

Properly prototype C function usage().
Sync usage() with the manual page: s/file/snapshot_name/g.

Close out a possible race where anybody in group operator could
chown an arbitrary file to operator.

Reported by: Ian Dowse <iedowse@maths.tcd.ie>
Sponsored by: DARPA & NAI Labs.

Add the mksnap_ffs command to the sbin directory. This setuid root
program allows users in the operator group to take filesystem
snapshots. Its first use will be in support of `dump -L'.

Approved by: Technical Review Board <trb@FreeBSD.org>
Sponsored by: DARPA & NAI Labs.