cpu/atmega_common: implement irq_is_enabled()
cpu/atmega_common: implement irq_is_enabled()

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