src: add support for character devices

It's working in my Linux machine. I don't know how it'll work for other OS

You can test this creating a character device just like this:
```
mknod  /tmp/my_device c 400 1
```
The problem is that you need to be root and I'm not sure if you want to run something like `sudo mknod ...` in the tests. In case you are ok I can add a couple of tests checking device creation / deletion