Handle specially the key of Float32x4Array and Int32x4Array element
storing for ARM and x64 port, use temp register instead of kScratchRegister
when calling AllocateSIMDHeapObject in x64 port.

This commit should be squashed with the previous commit.
Merge pull request #2 from fenghaitao/master

Handle specially the key of Float32x4Array and Int32x4Array element storing for arm and x64 port