- 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

By popular demand, move freebsd-version(1) from /libexec to /bin.

Approved by: re (gjb)

Introduce the /libexec/freebsd-version script, which is intended to be
used by auditing tools to determine the userland patch level when it
differs from what `uname -r` reports. This can happen when the system
is kept up-to-date using freebsd-update and the last SA did not touch
the kernel, or when a new kernel has been installed but the system has
not yet rebooted.

Approved by: re (glebius)