Run benchmarks with binaryen/wabt/wavm and potentially in browsers

@poemm began looking into this (although I don't think he's actually run any benchmarks yet). Per his update today:

Firefox advertises one pass wasm to native binary
Looked into Chakra (Microsoft’s engine), Webkits (Apple), V8 (Google), Spidermonkey (Firefox)
I believe Firefox is the best one
webkit has something close but has intermediate representation
Chakra does something very complicated
V8 has some directed graph based intermediate representation, loops correspond cycles in graph, many nested loops lead to a big slowdown
I read the Firefox source code, there’s a file https://dxr.mozilla.org/mozilla-central/source/js/src/wasm/WasmBaselineCompile.cpp, would be great if we can get it to run standalone, they advertise a single pass to binary which is exactly what we need
this isn’t testnet critical but useful for later
Casey: Guido thought there is a pretty simple patch for WAVM to make it bomb proof
WAVM might be another good way forward; it’s what we’re using for Hera
WAVM does use intermediate rep., for testing that’s fine but for production we may want something faster

ewasm / testnet