core/lifo: deprecate file for remove after 2021.04
core/lifo: deprecate file for remove after 2021.04

OTAkeys/RIOT,OlegHahm/RIOT,ant9000/RIOT,jasonatran/RIOT,ant9000/RIOT,RIOT-OS/RIOT,RIOT-OS/RIOT,kYc0o/RIOT,jasonatran/RIOT,OlegHahm/RIOT,OTAkeys/RIOT,miri64/RIOT,miri64/RIOT,kaspar030/RIOT,RIOT-OS/RIOT,OlegHahm/RIOT,kaspar030/RIOT,ant9000/RIOT,ant9000/RIOT,kYc0o/RIOT,OTAkeys/RIOT,OTAkeys/RIOT,kYc0o/RIOT,jasonatran/RIOT,OTAkeys/RIOT,authmillenon/RIOT,authmillenon/RIOT,miri64/RIOT,miri64/RIOT,jasonatran/RIOT,authmillenon/RIOT,RIOT-OS/RIOT,RIOT-OS/RIOT,OlegHahm/RIOT,authmillenon/RIOT,kaspar030/RIOT,jasonatran/RIOT,OlegHahm/RIOT,authmillenon/RIOT,kYc0o/RIOT,miri64/RIOT,authmillenon/RIOT,ant9000/RIOT,kaspar030/RIOT,kaspar030/RIOT,kYc0o/RIOT