MFC: r263881, r263952, r263983, r264068, r264090, r264131

Some xdev fixes:

- if TARGET_ARCH is not defined and XDEV_ARCH is defined then early define
  TARGET_ARCH to the valud of XDEV_ARCH: This allow the xdev-build target
  to be able to correctly chose the compiler it needs to build
- Allow overwriting XDTP to allow a user to not chose where the xdev env will
  live in
- Fix build for gcc only xdev (like ia64) by providing the proper -B to the
  toolchain and not relying on gcc being installed already in base
- Fix TOOLS_PREFIX so the generated toolchain has the right default sysroot when
  installed intead of getting the DESTDIR one
- Fix supporting DESTDIR
- Also overwrite CXX (needed for cross building c++ libraries with clang) and
  CPP (needed to cross build some libraries when gcc is the target default
  compiler but gcc is not installed on the building host)
- Prevent XDTP from being a relative path:
  XDTP is used as the default SYSROOT for clang and thus should be an absolute path.
- Respect default CC
MFC: r263948

Convert an unused banner from skeleton.c into a comment.
It is added to every generated files and fix build at certain warning level with clang 3.4

Submitted by:	Thomas Dickey <dickey@his.com> (byacc upstream)
Spotted by:	glebius
MFC r260607, r260610, r260934:

r260607:
The onyx codec works also as module, so add it.

r260610:
Described in the man page but not implemented. Here it comes,
atomic_swap_32/64. The latter only for powerpc64.

r260934:
Fix the resource information for the i2s-a node on certain G5 PowerMacs.
This is the first step needed to get the snapper codec working on those
machines.
The second step is to enable the corresponding I2S device and its clock.

Tested on machines where the snapper codec was already working, a G4 PowerBook
and a PowerMac9,1 with a Shasta based macio.
The PowerMac7,2/7,3 with a K2 based macio can now also play sound.
MFH (r263712): upgrade openssh to 6.6p1
MFH (r264308): restore p level in debugging output
Document r264377, OpenSSH update to 6.6p1.
While here, bump copyright year.

Todo: strip old entries from this file since 10.0-RELEASE.

Sponsored by:	The FreeBSD Foundation
Trim stale entries.
Use consistent <para>&nbsp;</para> for empty sections.

Sponsored by:	The FreeBSD Foundation
Clean up leading/trailing whitespace.
Rewrap paragraphs and long lines.

Sponsored by:	The FreeBSD Foundation
Remove reference to FreeBSD 6.2-R in the freebsd-update(8) note.
Rewrap.

Sponsored by:	The FreeBSD Foundation
Move OpenSSH entry to 'contrib' where it belongs.

Sponsored by:	The FreeBSD Foundation
MFC r263925
 Enable all cryptocaps because net80211 can do software encryption.