nativenet: Port nativenet for netdev

To test this, run

```
export BOARD=native
SENDER=0 make -C tests/netdev/ all flash && SENDER=1 make -C tests/netdev/ all flash && make -C tests/netdev/ test
```

~~Depends on #1492:~~ (it's merged)

```
* #1680
|\
… …
| |
| * #1448
| |\
* | | #1733
| * | #1732
| | * #1731
| |/
|/
* (master)
```
Quoting our reference coding conventions:

> When declaring pointer data or a function that returns a pointer type, the
> preferred use of '*' is adjacent to the data name or function name and not
> adjacent to the type name.  Examples:
>
>	char *linux_banner;
>	unsigned long long memparse(char *ptr, char **retptr);
>	char *match_strdup(substring_t *s);