3.8 Merge Request: r268673, r268531, r266833

[Daniel Sanders via llvm-commits]

Hi,

Is it ok to merge these three?
r268673 [MSan] [MIPS64] Fix vararg helper for >1 fixed argument.
r268531 [MSan] [Mips64] Add tests for vararg handling.
r266833 [Mips] [MSan] VarArgMIPS64Helper: Use target's endian, not host's.