Add a udev "Only use lirc" subpackage.

Adds a subpackage with an udev rule which disables all protocols
besides lirc. Kudos Anthony Messina, systemd mailing list.
Revise enabling of lirc protocol.

We have no way to know if an user needs to run the dreaded
"echo lirc > /sys(class/rc/rc0" command. We don't if if should be
run at all (e. g., usb-based RF devices) of it it's rc0, rc1 or
whatever.

Adds a configuration option which, if set, applies the command to
the configured device. Not nice, but the best we can do for now IMHO.
Spec: documenting upstream merge request.