If a function has children then the code object returned from __code__ must
contain an `mp_raw_code_t` (actually `mp_raw_code_truncated_t` is enough)
that points to the child table.
Signed-off-by: Damien George <damien@micropython.org>
This allows retrieving the code object of a function using
`function.__code__`, and then reconstructing a function from a code object
using `FunctionType(code_object)`.
This feature is controlled by `MICROPY_PY_FUNCTION_ATTRS_CODE` and is
enabled at the full-features level.
Signed-off-by: Damien George <damien@micropython.org>