Added a function for the slave to print received data.
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
OSX: fix readlink call
Merge pull request #1728 from mehlis/add_board_spark_core

added spark core board
Merge pull request #1878 from authmillenon/rpl_udp-16bit-addr

rpl_udp: Addresses must only be 8-bit with cc110x
added board airfy beacon
Merge pull request #1926 from mehlis/fix-readlink

OSX: fix readlink call
netdev: clarify documentation of netdev_driver_t::get_option()
Merge pull request #1928 from authmillenon/netdev-fix-doc

netdev: clarify documentation of netdev_driver_t::get_option()