Moved UART6 into a separate unit: UART6 connects internal devices. As a first step the existing code sections have been moved into a new unit. As well the code of the external GNSS sensor has been copied into this unit as starting point for the further development. Later the internal part can be integrated into the common uart (code cleanup).

Heinrichs Weikamp OSTC4 update files.

The builds are for testing purposes only. Be careful, they might not work and are definitely not recommended for real dives.