Merge branch 'develop' into fix/mqtt-buffer-overflow

arch/cpu/arm/cortex-m/Makefile.cortex-m

arch/cpu/arm/cortex-m/cm3/Makefile.cm3

arch/cpu/arm/cortex-m/cm4/Makefile.cm4

arch/cpu/cc2538/cc2538-def.h

arch/cpu/cc26xx-cc13xx/cc26xx.ld

arch/cpu/nrf52832/ld/nrf52-pca10036-sd.ld

arch/cpu/nrf52832/ld/nrf52-pca10040-sd.ld

arch/cpu/nrf52832/ld/nrf52.ld

arch/platform/cc2538dk/dev/board.h

arch/platform/openmote-cc2538/board.h

os/net/mac/tsch/tsch.h

tests/01-compile-base/Makefile

tests/02-compile-arm-ports-01/Makefile

tests/03-compile-arm-ports-02/Makefile