* makes `libdeno.shared` a `SharedArrayBuffer` instead of a regular `ArrayBuffer`.
* fixes `libdeno.shared` becoming undefined after accessing it once.
- Improves speed and binary size significantly.
- Makes deno_last_exception() output a JSON structure.
- Isolate::execute and Isolate::event_loop now return
structured, mapped JSError objects on errors.
- Removes libdeno functions:
libdeno.setGlobalErrorHandler()
libdeno.setPromiseRejectHandler()
libdeno.setPromiseErrorExaminer()
In collaboration with Ryan Dahl.
This is a large API refactor of deno.h which replaces
deno_send() and deno_set_response() with deno_respond().
It also adds a req_id parameter to the deno_recv_cb.
Make writeFile/writeFileSync use it.
