Benchmark update

Using the switches -O -release -inline actually do have an effect
like expected. Now the BCD implentation is faster than Phobos
in the small.
Updated BCD addition

Removing the dynamic memory allocation brings the large case down
to a reasonable execution time.
Regarding the addition algorithm
1) More tests need to be run to find possible holes in carry-over
   accross word boundaries
2) Need to test out the new code that does not dynamically allocate
   memory on each iteration through addition. There could be a
   possible one-off error. Need to think it through some more.
   So far it is working.
Cleaned up code

The first implementation of BIGINT is much slower than the BCD
implementation. Even a packed-binary implementation should
outperform the original one. So I removed it to clean up and
clarify intent to work on the BCD and PB implementations.