Add AUTHORS file
Update Debian package instructions: build unsigned package

(since I'm the only one who has the private key to sign the package)
Update credits in README
Ensure wiping of sensitive memory is not optimized away
Make sig_atomic_t variables volatile

Also use pointer instead of reference because I think it's more clear.
Implement privilege separation
Remove dead code
Merge tag '0.4' into debian
debian packaging: run in chroot and as rdiscd user
debian packaging: remove legacy ifupdown hooks from postinst
debian packaging: release 0.4-1