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
Revert "cpu/cc2538: sbrk() checks if the requested memory is really available."

This reverts commit 81dea364a5b372ad1625181eff710c095420735c.
cpu/nrf51822: changed ISR stack size to 512 byte
drivers/at86rf231: change to PLL_ON to change address
drivers/at86rf231: print raw packet when DEBUG_ENABLED
drivers/at86rf231: frame_type has to be set by upper layers
examples/default: print 16bit addresses
shell/transceiver: set 16 bit addresses and frame type
boards: adjusted TIMER_0 defines for NRF based b.

adjusted for
- pca10000
- pca10005
- yunjia-nrf51822
cpu/nrf51822: fixed timers

- changed TIMER_0 to be a 24-bit timer -> see Nordic PAN #32
- cleaned up timer initialization code
- added check if an interrupt channel was active
board/iot-lab_M3: added I2C ISR defines
cpu/stm32f1: fixes to i2c driver

- fixes BUSY on initialization
Merge pull request #1938 from haukepetersen/fix_stm32f1_morei2c

cpu/stm32f1: fixes to i2c driver
malloc: check if the requested memory is really available
resurrect malloc test
lsm303dlhc: initial import of lsm303dlhc driver

TODO: Accelerometer does not return valid values yet
Merge pull request #1782 from benpicco/fix_malloc

check if the requested memory is really available in _sbrk_r