Support basic AOT in BVM

[thosakwe]

1. Eager-analyze the module
2. Eager-compile all functions
3. Generate C++ file that:
   a. Creates a new BVM
   b. Creates a new BVMFunction with each function that has been compiled to bytecode.
   c. Calls execFunction with main
   d. Returns the correct exit code
4. Compile this using the user's compiler (allow passing extra args)
5. Spit out the native executable
6. Profit

[thosakwe]

This will require adding a little bit of abstraction to BVM, i.e letting it live without being tied directly to Dart. Not that difficult.