Optimize random number generator, bump version to 0.2.

Rework the random number generator based on sre-random. This includes
both executing speed and statistical improvement as well as much
higher precision for random floating point values. Several functions
have been added for optimized integer or floating point random number
generation with different precision levels.

Shift constants that indicate whether certain parameters are equal
to a power of two have been added to the FgenPopulation structure
(the FgenRNG structure has also seen some changes/additions). In
general, software using previous versions of libfgen should remain
compatible at the binary level as long as they do not directly access
certain fields in FgenRNG, and only allocate FgenPopulation structures
through fgen_create (which should normally be the case).

Bump version to 0.2.

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