LuaBcd

Implements an ADT for arbitrary large integers with the
arithmetic operators '+','-','/','*','^'.
The numbers are internally represented as binary coded
decimals (BCD) in blocks of 8 digits per 64 bit chunk.
The implementation is based on "BCD Arithmetic, a tutorial"
at http://homepage.divms.uiowa.edu/~jones/bcd/bcd.html.