db0c34d836
C99 has been the minimum required C standard version for Zephyr since its inception. After multiple attempts and discussions, a decision has been made to upgrade to C17 going forward. This commits replaces the default C standard from C99 to C17 in the configuration and build system, and deprecates support for the older standards. Signed-off-by: Carles Cufi <carles.cufi@nordicsemi.no>