problem with delay()-family

the onewire-lib is depending on proper timings, but the implementation of this board-lib does not work as expected. 

the original nrf52-library for the arduino primo uses the designated nrf-functions:
https://github.com/arduino-org/arduino-core-nrf52/blob/263c5bfb30a53e3d0cf995368c000cc1c49f8ca8/cores/arduino/delay.c
-> they seem to work as expected!
