networkd: remove unused variable
resolved: add a DNS client stub resolver

Let's turn resolved into a something truly useful: a fully asynchronous
DNS stub resolver that subscribes to network changes.

(More to come: caching, LLMNR, mDNS/DNS-SD, DNSSEC, IDN, NSS module)
update TODO
resolve: add distinct bus error code for hosts that exist but lack A or AAAA records
dns-domain: fix generation of reverse IP address lookup name
dns-domain: never allow labels that are larger than 63 chars
nss: various minor fixes to nss-myhostname + nss-mymachines
resolved: add small NSS module that uses resolved to resolve DNS names
update TODO
resolved: add legacy dbus service and policy files
resolved: add busname unit file
journal: allow files with no data whatsoever

If a file was opened for writing, and then closed immediately without
actually writing any entries, on subsequent opening, it would be
considered "corrupted". This should be totally fine, and even in
read mode, an empty file can become non-empty later on.
microhttp-util: rework gnutls logging
Move network-related journal programs to src/journal-remote/

Directory src/journal has become one of the largest directories,
and since systemd-journal-gatewayd, systemd-journal-remote, and
forthcoming systemd-journal-upload are all closely related, create
a separate directory for them.
build-sys: add check for libcurl
journal-remote: small fixes
journal-remote: reject fields above maximum size

Also fix an infinite loop on E2BIG.

Remember what range we already scanned for '\n', to avoid
quadratic behaviour on long "text" fields.
journal-upload: a tool to push messages to systemd-journal-remote
journal-upload: HTTPS support
journal-upload: use journal as the source