Improving UART futher; reducing footprint.
Cleaning up preprocessor sections.
Improving ADXL345 driver; adding missing configuration bitfields and values.

1. Removing dependency to IOStream.
2. Adding bitfield symbols.
Improving AT24CXX EEPROM driver; allow variable in psuedo section.

1. New macro EEPROM(nr) to set variable section and allow simple
addressing of data structures in EEPROM.
2. Update example sketch.