[Untranslated] Registering Functions

In order to register a function we need two things:

• we need to pass body of function we want to create in JavaScript as a string
• we need to get back a handle so we can call that function later with parameters

register_function(js:&str) -> usize

Since WebAssembly can only pass back and forth numbers, and since all numbers in JavaScript are 64-bit floats, what this will look like ultimately is an imported function:

register_function(js_start:f64,js_len:f64) -> f64

Underneath the covers we take advantage of JavaScript's eval function to make these functions real.