Update header file documentation, provide public log2 function

Update the member function documentation in the header file to
include the optimized repeating integer range functions. Also
provide CalculateLog2(n) (floor(log2(n)) and CalculateShift(n)
(return log2(n) only when n is a power of two) as public member
functions.

Remove some unused code.

Signed-off-by: Harm Hanemaaijer <fgenfb@yahoo.com>