Use custom Binaryen build, cleanup Wasm-related code

[Derppening]

This PR switches to our (my) personally maintained build of Binaryen, which is just the latest release with the parseTextWithFeatures API tacked on top of it. A regression test is also added for the parseText issue

The relevant PR in Binaryen's repository is here.

Also cleans up the Wasm-related code by:

• Using let for function locals
• Refactoring to use synchronous APIs when instantiating WebAssembly.Instance for execution

[LPTK]

Cool! But please push your changes to https://github.com/hkust-taco/binaryen and make the build point to that one instead.

[Derppening]

Cool! But please push your changes to https://github.com/hkust-taco/binaryen and make the build point to that one instead.

Could you also fork binaryen.js as well? This repo is the one that actually contains the npm wrappers over the JS API bindings.

[LPTK]

Right. Done! https://github.com/hkust-taco/binaryen.js

[Derppening]

Done in 6516cdd and e7d1cbc - We are using our own fork of binaryen now.