Add support for I32x4Neg, I32x4LtS, I32x4LeS, I32x4LtU, I32x4LeU, I16x8Splat,
I16x8ExtractLane, I16x8ReplaceLane, I16x8Neg, I16x8Shl, I16x8ShrS, I16x8ShrU,
I16x8Add, I16x8AddSaturateS, I16x8Sub, I16x8SubSaturateS for mips32 and mips64
architectures.

BUG=

Review-Url: https://codereview.chromium.org/2795143003
Cr-Commit-Position: refs/heads/master@{#45092}