tests: improve calculation in hwtimer_wait

Kudos to @Kijewski
iot-lab_M3: extend debug target for iot-lab_M3
SQUASHME: kill openocd by PID
Merge pull request #1628 from LudwigOrtmann/hwtimer_wait_fixup_2

tests: improve calculation in hwtimer_wait
native: add support for Linux on ARM
Merge pull request #1627 from LudwigOrtmann/native-arm

native: add support for ARM (Linux)
Merge pull request #1629 from thomaseichinger/iot-lab_debugger++

iot-lab_M3: extend debug target for iot-lab_M3
boards: initial import for HiKoB Agilefox
boards: use hikob_common for agilefox
boards: let iot-lab_M3 use hikob_common