Rework SPI error handling. SPI_Start_single_TxRx_with_Master evaluated the incoming data for a condition to send device instead of life data. In case of invalid input data this may cause unintended transmission of device data => now lifedata is send if incoming data is expected to be invalid The SPI timeout monitoring was done at the beginning of the mode loop. A timeout may have been detected even if meanwhile valid data was received (this is evaluated at x20ms) => Moved the timeout monitoring after the handling of incoming data

Imported from Ac6/SystemWorkbench/plugins/fr.ac6.mcu.firmware_1.14.7.201711101414/resources/builtin/:
* File syscalls.c