4445faaa3a
bitarithm.h is not needed for the interface of shed but may cause conflicts due to different definitions of SETBIT and CLRBIT common implementations are: (value, offset) xor (value, mask) bitarithm implements the later frac.c and nrf52/usbdev.c use bitarithm.h but where missing the include sam0/rtt.c defined a bit using mask from bitarithm, changed that to the soulution used in sam0/rtc.c