Merging r266833:

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r266833 | koriakin | 2016-04-20 00:46:59 +0100 (Wed, 20 Apr 2016) | 5 lines

[Mips] [MSan] VarArgMIPS64Helper: Use target's endian, not host's.

Ugh.

Differential Revision: http://reviews.llvm.org/D19292
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llvm-svn: 271119