Pull in r223171 from upstream llvm trunk (by Michael Zolotukhin):

  PR21302. Vectorize only bottom-tested loops.

  rdar://problem/18886083

This fixes a bug in the llvm vectorizer, which could sometimes cause
vectorized loops to perform an additional iteration, leading to possible
buffer overruns.  Symptoms of this, which are usually segfaults, were
first noticed when building gcc ports, here:

https://lists.freebsd.org/pipermail/freebsd-ports/2014-September/095466.html
https://lists.freebsd.org/pipermail/freebsd-toolchain/2014-September/001211.html

Since this fix is very important for ports, bump __FreeBSD_version to
make it easier for port maintainers to test whether the fix has been
applied.

Upstream PR:	http://llvm.org/PR21302
MFC after:	3 days
Move OFED init a bit earlier so that PXE boot works.

MFC after:	3 days
Sponsored by:	Mellanox Technologies
Apply chunk forgotten in r275620.  Remove local variable for real.

CID:	1257462
Sponsored by:	The FreeBSD Foundation
Do not call VFS_SYNC() before VFS_UNMOUNT() for forced unmount.

Since VFS does not/cannot stop writes, sync might run indefinitely, or
be a wrong thing to do at all.  E. g. NFS ignores VFS_SYNC() for
forced unmounts, since non-responding server does not allow sync to
finish.  On the other hand, filesystems can and do stop writes using
fs-specific facilities, and should already fully flush caches in
VFS_UNMOUNT() due to the race.

Adjust msdosfs tp sync in unmount for forced call, to accomodate the
new behaviour.  Note that it is still racy, since writes are not
stopped.

Discussed with:	avg, bjk, mckusick
Reported and tested by:	pho
Sponsored by:	The FreeBSD Foundation
MFC after:	3 weeks
Include sys/kernel.h to pick up the definition of hz. subr_syscall.c uses
it after r275616.

X-MFC with:	r275616
Update the virtio driver to work on the ARM AArch64 Foundation Model.
There are two main parts to get it to work, 1) most of the register
accesses need to be word sized, other than the config register which
needs to be byte aligned, and 2) we don't need the platform driver
for this to work on the Foundation Model, allow it to be NULL.

Differential Revision:	https://reviews.freebsd.org/D1240
Reviewed by:	bryanv
Sponsored by:	The FreeBSD Foundation