WebAssembly / js-types

WebAssembly JS and Web integration spec in Bikeshed (#591)
* WebAssembly JS integraton spec in Bikeshed

Initial checkin, JS.bs is converted from JS.md with
updates to reference the current Wasm specification.

* Various cleanups/fixes:

- Ensure that not passing a maximum Memory size in the object will not
  create a maximum in Wasm.
- Clean up notes about object deduplication in instantiate.
- Refer to Promises guide everywhere.
- Remove duplicate buffer cloning.

* Improve threading

* Initial checkin of web interface

* Name WebAssembly CG as the editor (I'm not sure who should be editor)

* Fix formatting and queue instantiate(module) tasks appropriately

* Changes based on review from @domenic, @rossberg and @binji

* More changes from review by @domenic and @rossberg

* More changes from review

* Move

* More changes from review

- Formalize the process of getting a name for exported functions (including
  passing on the name of re-exported host functions)
- Link to ECMAScript bug for Memory detach behavior
- Some wording clarifications
- Extract out creation of a host function for clarity

* More precise wording for decoding success assertion

* Move specs to index.bs

* Respond to review feedback

* Respond to review from @annevk

* Respond to review from @lukewagner

[interpreter] Add missing dependency to install target (#588)

Disallow using internal globals in constant expressions (#383)