gnrc_sock: set remote network interface implicitly

pkg: ccn-lite: minor changes to integrate latest ccn-lite features

tools: show diff for headerguards check on failure

boards/nucleo-l452: initial support

unittests/tests-littlefs: fix dummy mtd

mtd_spi_nor: make thread safe

README: cleanup in tap network section

When there is only one interface we are simplifying a lot for the users
if the interface is set implicitly.

    fixes #8737

pkg: update littlefs pkg to v1.3

_init function were erasing whole memory leading to losing everything
when mounting or formating the memory

tools/ci: enhance print_toolchain script

tests/periph_uart: included power_on/off() in test

    - add generic command version printer
    - add cmake version
    - enhance output structure

info-build: add INCLUDES to the output

boards/nz32-sc151: fix ingroup directive in periph_conf

cpu+board: Add support for NXP Kinetis KW41Z and FRDM-KW41Z development board

https://www.nxp.com/products/processors-and-microcontrollers/arm-based-processors-and-mcus/kinetis-cortex-m-mcus/w-serieswireless-conn.m0-plus-m4/freedom-development-kit-for-kinetis-kw41z-31z-21z-mcus:FRDM-KW41Z

kinetis: Set LPUART clock source during uart_lpuart_init