restartable netdde

[Samuel Thibault]

Hello,

One nifty feature of userland drivers is that you can easily restart
them by just making the translator away. However, that makes pfinet
away, as well as all current network connexions and listening servers.

But pfinet doesn't really need to exit: it could just reopen the network
device after e.g. 1s delay, reconfigure it, and continue as if nothing
happened.

Could somebody have a look?

Samuel