sys/newlib_syscalls_default: mark _exit as used
sys/newlib_syscalls_default: mark _exit as used

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