Async event loop to disable Emterpreter

[rhysd]

As described in known issues, disabling Emterpreter would make execution more stable and faster. For that, an event loop for waiting user input must be async to use JavaScript's setTimeout().

[curiousdannii]

You should at least use a whitelist.

[rhysd]

Yeah, I want to use it, but emcc crashes on compilation.

[rhysd]

I could identify which function caused the emcc crash and could enable whitelisting. I added a whitelist at 2df338e though it might not be perfect. Now all functions which are not listed in the list are compiled to wasm directly.

[rhysd]

This was fixed by #30. Emterpreter is no longer used. So we don't need to rewrite functions to async.