Merging r182486:

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r182486 | d0k | 2013-05-22 10:01:12 -0700 (Wed, 22 May 2013) | 3 lines

X86: When expanding PCMPGTQ to PCMPGTD we always want to compare the lower halves as unsigned.

Take #2 on fixing PR15977.
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llvm-svn: 182489