package/sysklogd: add systemd services

Sysklogd had only SYSV init scripts. Add systemd service files to start
klogd and syslogd.

Signed-off-by: Petr Kulhavy <brain@jikos.cz>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>