- 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

Note that a UFS filesystem can have up to 20 active snapshots.

PR: docs/151104
Submitted by: Aldis Berjoza <aldis@bsdroot.lv>
MFC after: 3 days

mdoc: move CAVEATS, BUGS and SECURITY CONSIDERATIONS sections to the
bottom of the manpages and order them consistently.

GNU groff doesn't care about the ordering, and doesn't even mention
CAVEATS and SECURITY CONSIDERATIONS as common sections and where to put
them.

Found by: mdocml lint run
Reviewed by: ru

Fix an xref.

PR: 138833
Submitted by: Alex Keda <admin@lissyara.su>
MFC after: 3 days

- 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.

Note that snapshots may cause a panic on the full UFS filesystem.

Submitted by: pho
MFC after: 3 days

Replace a reference to non existant mount_ffs(8) by a reference to mount(8).

mdoc(7) fixes.

Approved by: re (blanket)

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.