resolved: we don't need the DNS server "source" concept anymore, remove it
sd-network: make socket filter programs static const where possible

(also, fix some whitespace/indentation issues, and avoid "index" as identifier in
order to not clash against libc's "index()" call)
resolved: set LLMNR TCP and UDP TTLs to the values suggested by the RFC
resolved: add more debug logging
resolved: the llmnr destination address check applies to queries, not to responses