doc: add license headers to some .h files

boards/native/include/board_internal.h

core/include/kernel_types.h

cpu/native/include/native_internal.h

sys/include/auto_init.h

sys/include/bloom.h

sys/include/board_uart0.h

sys/include/chardev_thread.h

sys/include/hash_string.h

sys/include/ping.h

sys/include/ps.h

sys/include/random.h

sys/include/shell_commands.h

sys/include/timex.h

sys/include/tm.h

sys/include/transceiver.h