[SIMD.js] Refactor the simd128 registers in deoptimizer

Only replace double registers with simd128 registers on architectures that
support this. Currently they are ia32, x64 and arm.
Merge pull request #62 from huningxin/fix-simd-reg-deoptimizer

[SIMD.js] Refactor the simd128 registers in deoptimizer