Currently, the init script would kill itself

TODO: Partially autogenerate from README.client too.

Can be disabled in common.h in case your kernel does not support it.

Pointed out by Stick.

sendmsg() with only ancilliary message does not work, apparently.
Therefore, to make things cleaner, pass command/reply directly using
sendmsg() instead of newline-terminated strings.

Complete basic implementation, compiles but not tested yet.