Added a function for the slave to print received data.
cpu/stm32f4: optimized GPIO driver implementation
SQUASH: cpu: fixed some typos
SQUASH: cpu/f4: changed order of irq enabling seq
Only read pan ID when address mode is not 0, when reading 802.15.4 header
make: remove dependency from flash to all

* print message when no hex file is found instead
* add objcopy for native so that flash can succeed
Merge pull request #1724 from LudwigOrtmann/flash-all

make: remove dependency from flash to all
Merge pull request #1802 from Troels51/ieee-802.15.4-frame-format-fix

fix in ieee 802.15.4 frame
boards: add `extern "C"` to header files
Merge pull request #1806 from BytesGalore/extern_C_in_headers_boards

boards: add `extern "C"` to header files
drivers/mq3: add extern "C" to header
Merge pull request #1918 from LudwigOrtmann/1703-fixup

drivers/mq3: add extern "C" to header
drivers/at86rf231: fix two cppcheck findings
cpu/stm32f0: optimized GPIO driver implementation
Merge pull request #1865 from haukepetersen/fix_stm32f0_gpioremodel

cpu/stm32f0: optimized GPIO driver implementation
Merge pull request #1920 from thomaseichinger/at86_fix

drivers/at86rf231: fix two cppcheck findings
added spark core board
auto_init: adapt auto_init for cc110x devices
rpl_udp: Addresses must only be 8-bit with cc110x
rpl_udp: optimize error handling for set command