Initial import of i2c lowlevel driver for stm32f4
Merge pull request #1859 from PeterKietzmann/add_stm32f4_i2c

cpu/stm32f4: added i2c driver implementation
cpu: moved reboot_arch for cortex cpus
cpu/cortex-mX_common: fixed reboot_arch return val
cpu/cortex-mX_common: added delay to reboot_arch
cpu/lpc1768: heavy clean-up of existing code

- moved to new port structure
- rewrote startup code
- added implementation dummies for UART and timer
- switched to atmel linkerscript
- cleaned up Makefiles
board/mbed_lpc1768: heavy clean-up

- removed legacy code
- added default defines
- created periph_conf.h
Initial import of the updated srf02 driver with general i2c interface
Merge pull request #2045 from haukepetersen/fix_board_mbed

board/mbed_lpc1768: remodeled to our board/cpu structure
Merge pull request #1871 from PeterKietzmann/add_srf02_general_i2c_if

drivers/srf02: adapted ultrasonic ranger driver to general i2c interface
Merge pull request #2047 from haukepetersen/fix_cortex_reboot

cpu: fixed and moved reboot_arch for cortex cpus
tests: define random default GPIOs to pass Travis builds
Merge pull request #2064 from thomaseichinger/sensor-features

tests: define random default GPIOs to pass Travis builds
tests: fix tests/posix_semaphore
posix: Fix missing `restoreIRQ()` in `sem_post()`