doc: fix doc hierarchy

sys: fmt: add fmt_lpad()

Driver: add HD44780 LCD support

drivers/feetech : initial support

boards/nucleo: include arduino pinmap in board definitions

tests: enhance xtimer_now64_continuity

Sema: Fix Typo related to return values in documentation.

    - adapt code to use public, typesafe API calls
    - add some statistical output
    - minor code enhancements and doc corrections
    - use fmt print_str for uint64_t

kinetis: Refactor interrupt vector definition

boards/nucleo144-f429: initial support

... to match the vector definition in other Cortex-M platforms

make: Add support for specifying a different compiler for assembler

LLVM toolchain: set CFLAGS for pkgs

    - set no-gnu-zero-variadic-macro-arguments
    - set no-unused-function

    - set no-keyword-macro
    - set no-parentheses-equality

pkg: jerryscript: initial import & example Jerryscript Javascript interpreter

cpu: native: make syscalls vfs ready (introduce real_fcntl)

shell_commands: fix sc_vfs warnings

nrf24l01p: add disable crc function