Pull in r211435 from upstream llvm trunk (by Benjamin Kramer):

  Legalizer: Add support for splitting insert_subvectors.

  We handle this by spilling the whole thing to the stack and doing the
  insertion as a store.

  PR19492. This happens in real code because the vectorizer creates
  v2i128 when AVX is enabled.

This fixes a "fatal error: error in backend: Do not know how to split
the result of this operator!" message encountered during compilation of
the net-p2p/libtorrent-rasterbar port.

Reported by:	Evgeniy <iron@mail.ua>
MFC after:	3 days
Add the llvm patch for r267704.
Allow creation of SDT probes from a module in which no providers are
defined. This ensures that the sdt:zfs:: probes appear despite the fact
the sdt provider is defined in the kernel rather than in zfs.ko.

Reported by:	hiren
Tested by:	hiren
MFC after:	2 weeks
do_dup: plug redundant adjustment of fd_lastfile

By that time it was already set by fdalloc, or was there in the first place
if fd is replaced.

MFC after:	1 week
fd: replace fd_nfiles with fd_lastfile where appropriate

fd_lastfile is guaranteed to be the biggest open fd, so when the intent
is to iterate over active fds or lookup one, there is no point in looking
beyond that limit.

Few places are left unpatched for now.

MFC after:	1 week
Add note on SYSCTL VARIABLES.
add support for MosChip MCS9922...  This is found on an ExpressCard..

tested to work w/ cu talking to itself (the two ports connected via
null modem cable)...
more of the same
remaining libc stuff