Rewrote bcd.c to allow for changing the size of the significand.
Rewrote bcd.c to allow for changing the size of the significand.

This is a major rewrite of bcd.c.  It now breaks the significand down
into 32-bit chunks.  You can use a significand that is a multiple of 8
digits.

joeriggs/experiments,joeriggs/experiments,joeriggs/experiments,joeriggs/experiments