-Algorithm used:
-calibrateOscillator() first does a binary search in the OSCCAL register for
-the best matching oscillator frequency. Then it does a next neighbor search
-to find the value with the lowest clock rate deviation. It is guaranteed to
-find the best match among neighboring values, but for version 5 oscillators
-(which have a discontinuous relationship between OSCCAL and frequency) a
-better match might be available in another OSCCAL region.