- added SPI_DEV and SPI_UNDEF macros
- made types and speed values overritable by CPU
- moved old device enum to dev_enums.h
- reformatted a little bit to comply to 80 char line length
- unify file/module @brief
- distinct @file section more visibly in source
- provide missing @brief's
- move module details/notes from file to module sections
- provide missing macro definition for building