Update the simd.js

It bases on
https://github.com/johnmccutchan/ecmascript_simd/blob/b5dce3a7039a6d38cb7922f526cdb49a69f01dc5/src/ecmascript_simd.js

API changes:
* Added shiftLeft, shiftRightLogical, shiftRightArithmetic on int32x4.
* Added equals, greaterThan, and lessThan that operate on int32x4.
* Add bit operations (and, or, xor, and not) that operate directly on float32x4.
* Moved constructors into SIMD module.
* Remove use of "new float32x4" and "new uint32x4"
Move float32x4 and int32x4 constructors into SIMD module.