- 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

Don't let hastd use C11 atomics.

Due to possible concerns about the stability of C11 atomics, use our
existing atomics API instead.

Requested by: pjd

Let hastd use C11 atomics.

C11 atomics now work on all the architectures. Have at least a single
piece of software in our base system that uses C11 atomics. This
somewhat makes it less likely that we break it because of LLVM imports,
etc.

Partially revert my last change.

I forgot that I still had a locally applied patch to my copy of Clang
that needs to be pushed in before we should use C11 atomics.

Use C11 <stdatomic.h> instead of our non-standard <machine/atomic.h>.

Reviewed by: pjd

- Add support for 'memsync' mode. This is the fastest replication mode that's
why it will now be the default.
- Bump protocol version to 2 and add backward compatibility for version 1.
- Allow to specify hosts by kern.hostid as well (in addition to hostname and
kern.hostuuid) in configuration file.

Sponsored by: Panzura
Tested by: trociny