Merge pull request #1765 from LudwigOrtmann/feature_gpio

boards/arduino-due/Makefile.features

boards/arduino-mega2560/Makefile.features

boards/iot-lab_M3/Makefile.features

boards/msbiot/Makefile.features

boards/pca10000/Makefile.features

boards/pca10005/Makefile.features

boards/samr21-xpro/Makefile.features

boards/stm32f0discovery/Makefile.features

boards/stm32f3discovery/Makefile.features

boards/stm32f4discovery/Makefile.features

boards/udoo/Makefile.features

boards/yunjia-nrf51822/Makefile.features

tests/driver_pir/Makefile

tests/periph_gpio/Makefile

tests/periph_gpio_exti/Makefile