This commit is a fairly large refactor, mainly because it unified the
two different ways that existed to represent references.
Now Reference values are also a kind of value.
It also implements a printer for values/references instead of copying
the implementation everywhere.
As the parser now flattens out the instructions and inserts synthetic
nesting/structured instructions where needed, we can treat the whole
thing as a simple parsed bytecode stream.
This currently knows how to execute the following instructions:
- unreachable
- nop
- local.get
- local.set
- {i,f}{32,64}.const
- block
- loop
- if/else
- branch / branch_if
- i32_add
- i32_and/or/xor
- i32_ne
This also extends the 'wasm' utility to optionally execute the first
function in the module with optionally user-supplied arguments.
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.
