- 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

Fix typos in the BSD License.

Do not inherit $SYSRC_VERBOSE from operating environment. The concern is
that when a user (such as myself) which has SYSRC_VERBOSE=1 in his/her
~/.bash_profile or such that when they are told to execute a command like:

hostname `sysrc -n hostname`

NOTE: To activate a recently configured hostname.

If $SYSRC_VERBOSE is set, then POLA is violated because the output of sysrc
is indirectly influenced (making for an inconsistent experience).

Mirror the changes made in SVN r240798:

Replace "( : ${var?} )" syntax with better "[ ${var+set} ]" syntax.

Reviewed by: adrian (co-mentor)
Approved by: adrian (co-mentor)

Import sysutils/sysrc from the ports tree (current version 5.1). Importing
disconnected under the WITH_BSDCONFIG flag (a good idea since this version of
sysrc(8) indeed requires the `sysrc.subr' module installed by bsdconfig(8)).

Multiple reasons sysrc should not simply continue to live in ports. The most
important being that it is tightly coupled with the base.

Approved by: adrian (co-mentor)