Added a function for the slave to print received data.
net_if: alternative approach for swapping the byte order
tests/periph_adc: added test for adc driver
core: msg_receive should yield

If a thread sends blocking, but the target thread is not currently in
receive mode, the sender gets queued. If it has a higher priority it
should run again as soon as the target goes into receiving mode.
cpu/stm32f0: added missing features to Makefile
Merge pull request #1955 from haukepetersen/fix_stm32f0_addfeatures

cpu/stm32f0: added missing features to Makefile
Merge pull request #1835 from OlegHahm/msg_receive_yield

core: msg_receive should yield
Merge pull request #1951 from haukepetersen/add_test_periphadc

tests/periph_adc: added test for adc driver
Merge pull request #1826 from PeterKietzmann/extend_test_periph_spi

tests/periph_spi: print rx-buffer on slave
Merge pull request #1948 from OlegHahm/netif_byteorder

Netif fix byteorder
auto_init: always set source address mode
Merge pull request #1957 from OlegHahm/auto_init_addr_mode

auto_init: always set source address mode
boards: initial import for HiKoB Agilefox