Pull in r211627 from upstream llvm trunk (by Bill Schmidt):

  [PPC64] Fix PR20071 (fctiduz generated for targets lacking that
  instruction)

  PR20071 identifies a problem in PowerPC's fast-isel implementation
  for floating-point conversion to integer.  The fctiduz instruction
  was added in Power ISA 2.06 (i.e., Power7 and later).  However, this
  instruction is being generated regardless of which 64-bit PowerPC
  target is selected.

  The intent is for fast-isel to punt to DAG selection when this
  instruction is not available.  This patch implements that change.
  For testing purposes, the existing fast-isel-conversion.ll test adds
  a RUN line for -mcpu=970 and tests for the expected code generation.
  Additionally, the existing test fast-isel-conversion-p5.ll was found
  to be incorrectly expecting the unavailable instruction to be
  generated.  I've removed these test variants since we have adequate
  coverage in fast-isel-conversion.ll.

This is needed to compile clang with debug+asserts on older powerpc64
and ppc970 targets.

Requested by:	jhibbits
MFC after:	3 days