- Copy stable/10@296371 to releng/10.3 in preparation for 10.3-RC1
builds.
- Update newvers.sh to reflect RC1.
- Update __FreeBSD_version to reflect 10.3.
- Update default pkg(8) configuration to use the quarterly branch.

Approved by: re (implicit)

MFC r274073:
Follow-up to r255036; remove beforeinstall directives from bsdconfig(8)
Makefile's, fixing concurrent installworld (`make -j17 installworld').

Reviewed by: delphij
Thanks to: delphij, emaste

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Add debugging (for a case that shouldn't arise, but makes it more obvious
if a menu addition is made in one plce but forgotten in another).

Lessen verbosity of "Exit" menutag items to appear more consistent across
menus from one module to the next.

Replacing "Exit this menu (returning to previous)" with "Exit this menu".

PR: ports/169316

Resurrect usage.hlp and securelevel.hlp from sysinstall(8) and integrate them
into bsdconfig(8).

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

Import bsdconfig(8) as a replacement for the post-install abilities of
deprecated sysinstall(8). NOTE: WITH_BSDCONFIG is currently required.

Submitted by: Devin Teske (dteske), Ron McDowell <rcm@fuzzwad.org>
Reviewed by: Ron McDowell <rcm@fuzzwad.org>
Approved by: Ed Maste (emaste)