drivers: Initial import of SPI low-level driver IF
drivers: fixes to the SPI low-level interface
driver: updated SPI driver interface
[SQUASH ME] added fixed speed values
[SQUASH ME] removed UNDEFINED from device list
[SQUASH ME] fixed signature of spi_transfer_reg()
[SQUASH ME] added begin_transaction, fixed doc
native: reenable compilation on osx
core:queue: remove ancient example
queue: remove inttypes clutter from core header
queue: remove unused generic functions

Closes #1153.
queue: add queue_t root type
avsextrem: use cc110x_ng as default transceiver driver
Merge pull request #1115 from Kijewski/queue-cleanup

core:queue: clean up queue
Merge pull request #1496 from LudwigOrtmann/osx-fixup

native: reenable compilation on osx
tests: remove `test_` prefix

Closes #1485.
tests: fix APPLICATION name
Merge pull request #1503 from phiros/avsextrem_default_transceiver_cc110x_ng

avsextrem: use cc110x_ng as default transceiver driver
Merge pull request #1502 from Kijewski/issue-1485

tests: remove `test_` prefix
make: force traversal into PKG's, same as normal modules