Following code used to fail due to the way used to define
os.open in rust. To fix this, we need to use `FromArgs`
to define `struct OpenArgs {...}`.
```
f = os.open(path=__file__, flags=os.O_RDONLY, mode=0o777, dir_fd=None)
```
Noted that the original `open` is now rename to `os_open`
and is exported as `open`.
Related to #1175