Provide access to table exports and registering extra functions.

[basicer]

This would allow calling function that expect to be passed a c function pointer argument.

[ashtonmeuser]

This is a great next step. I'm imagining starting with supporting only exported WebAssembly tables via the following API. Please let me know your thoughts.

New class WasmTable with the following structure.

class WasmTable:
  bool import;
  func get(index: int);
  func set(index: int, func: Callable);

Tables accessible via Wasm.table(table_name).

In the future, this could support import tables via an import dictionary as follows.

imports = {
  functions: { ... },
  memory: ...,
  tables: {
    "my_table": my_table,
  },
}