gnrc_sixlowpan_iphc: cleanup NHC encoding

boards: Harmonized UART config of Nucleo-64 boards

boards/stm32f103c8: update flash flags for DFU

nimble: deactivate -Wunused-function with LLVM/clang

When building `nimble` with LLVM/clang the function
`ble_ll_adv_active_chanset_is_sec()` in `ble_ll_adv.c` is reported to
be unused, it is used within an assertions and `ifdef`s within that
file though. So this just disables that warning.

make: provide support for listing supported and blacklisting toolchains

Assuming `TOOLCHAIN_SUPPORTED` is provided by the board and
`TOOLCHAIN_BLACKLIST` by a module or `pkg`, this outputs the fact that
a toolchain is not supported or blacklisted in a similar manner as
(un-)supported features and boards are.

 dist: move testrunner to pythonlibs as package 

The latest bootloader has new usb device id and needs different
parameters to flash a RIOT image using `dfu-util`.

- nucleo-f334r8:
  - Added USART1 and USART3 config
- nucleo-f401re:
  - Changed order of UARTs to match the other boards
- nucleo-f410rb:
  - Added USART6 configuration
  - Fixed incorrect DMA settings (according to reference manual of the MCU)
- nucleo-f446re:
  - Changed order of UARTs to match the other boards
- nucleo-l152re:
  - Changed order of UARTs to match the other boards

The result of this harmonization is, that the first UART is always USART2, the
other USARTs are added in ascending order.

pkg: cmsis-dsp: fix -Wunknown-attributes for LLVM

Apparently LLVM doesn't know the `optimize` attribute.

boards/sensebox: Add support for SenseBox board

make: Makefile.include: Remove -Wno-implicit-fallthrough

frdm-k64f: Add SAUL ADC configuration

frdm-k64f: Update ADC configuration 

cpu/lpc2387: Fixed documentation and bugs preventing use of LLVM

pkg/ccn-lite/relic: check for minimal cmake version

- Previous cast was to a function pointer was not legal
- Using already present function pointer to store the IAP entry point to improve
  readability. (Which also fixes the cast issue.)

relic does not build with cmake < 3.6.0. This checks for a minimal version
instead of failing to compile.

    cmake version 3.5.2 is not >= to minimal required 3.6.0

    Makefile:25: recipe for target '..cmake_version_supported' failed

ccn-lite does not build with cmake < 3.6.0. This checks for a minimal version
instead of failing to compile.

    cmake version 3.5.2 is not >= to minimal required 3.6.0

    Makefile:25: recipe for target '..cmake_version_supported' failed

Tested with versions 3.5.2, 3.6.0-rc1, 3.6.0, 3.6.3, 3.7.0-rc1, 3.7.0.

Note: the check used does not consider '-rcX' as 'sort -V' does not handle them
properly.

    usage: has_minimal_version.sh <version> <minimal_version> [toolname]
      Checks that version >= minimal_version
      Version format MAJOR.MINOR.PATCH ex 3.1.4

gnrc/6lo: Set more data flag on all but last fragment

stm32_common/eeprom: fix DEBUG formatting

This fixes compilation for `periph_eeprom` with LLVM/clang and also is
more in accordance with our [coding conventions].

[coding conventions]: https://github.com/RIOT-OS/RIOT/wiki/Coding-conventions#-wformat

boards: slstk3402a: add i2c

- arm_reset was completely undocumented, even though technical details buried
  deeply in the data sheet of the LPC2387 are involved in the code
- The attribute "naked" is misplaced, it should only be used when no C code
  is present. However, the function consists of C code only
- The attribute "noreturn" has to be used in the declaration [1] of a function,
  not in the implementation. Otherwise the caller is not informed and code using
  the function will not be optimized.

[1]: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html