Previously, this was parsing only one kind because I mistakenly assumed
that they all had the same shape, now it can parse two kinds, and will
return NotImplemented for the rest.
This adds very basic support for module instantiation/allocation, as
well as a stub for an interpreter (and executions APIs).
The 'wasm' utility is further expanded to instantiate, and attempt
executing the first non-imported function in the module.
Note that as the execution is a stub, the expected result is a zero.
Regardless, this will allow future commits to implement the JS
WebAssembly API. :^)
