stm32f30x/pios_i2c: fixed PIOS_I2C_EV_IRQ_Handler diagnostics
stm32f30x/pios_i2c: removed unused TransferCallback api function
stm32f30x/pios_i2c: use pios_mutex for bus locking, was pios_semaphore
stm32f30x/pios_i2c: fixed event overflow by removing excess PIOS_IRQ_Disable calls
stm32f30x/pios_i2c: fixed possible data race in I2C_Transfer
stm32f4xx/pios_i2c: use pios_mutex for bus locking, was semaphore
stm32f4xx/pios_i2c: fixed possible data race in I2C_Transfer
stm32f10x/pios_i2c: use pios_mutex for busy locking, was semaphore
stm32f10x/pios_i2c: fixed possible data race in I2C_Transfer
Merge pull request #1247 from lilvinz/i2c_fixes

I2c fixes