Move float32x4 and int32x4 constructors into SIMD module.

It is according to
https://github.com/johnmccutchan/ecmascript_simd/blob/b5dce3a7039a6d38cb7922f526cdb49a69f01dc5/src/ecmascript_simd.js
1.19.0
Handle the phi when generating SIMD codes.
1.19.1
Merge pull request #34 from huningxin/update_simd

Move float32x4 and int32x4 constructors into SIMD module.
Merge pull request #35 from huningxin/simd_phi

Handle SIMD phi
rip out no longer needed hacks to redirect library functions ; 1.19.2
1.20.0
1.21.0
1.21.1
1.21.2
1.21.3
fix #41
fix
1.21.4
Merge pull request #43 from coolwanglu/fix

fix #41
queue phi changes for all parts of legalizing switches, as they may not be ready yet; fixes emscripten#2539
1.21.5
1.21.6
Support Asyncify