afsocket: Warn & auto-migrate when using /dev/log under systemd

We were emitting a warning when /dev/log was in use, yet, we were
running under systemd, but only when the config version was older than
3.4. Due to various circumstances, lets extend that so it warns on 3.5
too.

Requested-by: Peter Czanik <czanik@balabit.hu>
Signed-off-by: Gergely Nagy <algernon@balabit.hu>
filter: Allow in-list("FILE", value("MACRO"))

While the in-list("FILE", value("MACRO")) syntax was documented in the
commit message, it was not actually supported. This patch implements
that syntax too.

Signed-off-by: Gergely Nagy <algernon@balabit.hu>
afstomp: Make it depend on libsyslog-ng.la

For parallel builds, depend on ${MODULE_DEPS_LIBS}, to avoid a race
condition.

Signed-off-by: Gergely Nagy <algernon@balabit.hu>
value-pairs: Fix a crash when an invalid scope is specified

Terminate the list of scopes with empty values, so we reach the stop
condition instead of overflowing.

Signed-off-by: Gergely Nagy <algernon@balabit.hu>