Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

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

MFC r234353:

Upgrade our copy of llvm/clang to trunk r154661, in preparation of the
upcoming 3.1 release (expected in a few weeks). Preliminary release
notes can be found at: <http://llvm.org/docs/ReleaseNotes.html>

MFC r234982:

Upgrade our copy of llvm/clang to r155985, from upstream's release_31
branch. This brings us very close to the 3.1 release, which is planned
for May 14th.

MFC r235058:

Make sure a few new internal clang headers get installed, I missed these
in the last import. They are sometimes needed when you want to use
advanced instructions.

Also, add clang's internal stdalign.h header to ObsoleteFiles.inc, since
it is redundant: we already have a stdalign.h header in /usr/include.

Pointy hat to: dim
PR: kern/167574
Submitted by: jkim
Reported by: Oliver Hartmann <ohartman@zedat.fu-berlin.de>

Upgrade our copy of llvm/clang to trunk r154661, in preparation of the
upcoming 3.1 release (expected in a few weeks). Preliminary release
notes can be found at: <http://llvm.org/docs/ReleaseNotes.html>

MFC after: 2 weeks

Vendor import of clang trunk r154661:
http://llvm.org/svn/llvm-project/cfe/trunk@r154661