Merge pull request #6345 from aabadie/nucleo-f031

boards/nucleo32-f031/Makefile

boards/nucleo32-f031/Makefile.dep

boards/nucleo32-f031/Makefile.features

boards/nucleo32-f031/Makefile.include

boards/nucleo32-f031/board.c

boards/nucleo32-f031/dist/openocd.cfg

boards/nucleo32-f031/include/board.h

boards/nucleo32-f031/include/gpio_params.h

boards/nucleo32-f031/include/periph_conf.h

cpu/stm32f0/include/cpu_conf.h

cpu/stm32f0/include/stm32f031x6.h

cpu/stm32f0/ldscripts/stm32f031k6.ld

examples/dtls-echo/Makefile

examples/gcoap/Makefile

examples/gnrc_border_router/Makefile

examples/gnrc_minimal/Makefile

examples/gnrc_networking/Makefile

examples/gnrc_tftp/Makefile

examples/ipc_pingpong/Makefile

examples/microcoap_server/Makefile