drivers/at86rf231: refactoring of the at86rf231 radio driver

* deploy extended operation mode
* cleanup
* implement netdev 802154.h interface
netdev/802154: suppress cppcheck warnings in 802154.h

Suppress cppcheck warnings of class unusedStructMember because
this interface is not used yet. Remove these comments once it
is used.
Merge pull request #1846 from thomaseichinger/at86rf23x

drivers/at86rf231: refactoring of the at86rf231 radio driver
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
OSX: fix readlink call