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
lsm303dlhc: initial import of lsm303dlhc driver

TODO: Accelerometer does not return valid values yet
cpu/stm32f1: fixes to i2c driver

- fixes BUSY on initialization