The comments should be internal
Prepare to change operator functions to work on word arrays
Fix a comment
Change the add internal API

adc and add now target positive addition only (a corresponding set
of subtraction routines will be added later). add now modifies
the left hand value in-place and avoids memory allocation when
possible to do so safely.
Completed the integration of the new addition functionality

I am not sure if pure and @safe should be used on constructors.
They are used at the moment to allow the ctor to be used by
opBinary.
Removed the need for the extra attributes on the ctor
Implement add using rvalues
Calculate the overflow separately
Fix addition of Bcd15 values
Added a function to clear the overflow digit
Fixed addition of an array of BCD-15 digits
Fixed addition of Integer values
More addition tests

Test addition for unevenly sized arrays where the extra space in
either the augend or the addend does not matter.
Improve the debug printing of BCD-15 word arrays
Updated subtraction; not fully working
Some infrastructure for multiplication
Merge pull request #99 from joichiro/i98

Integer operators should perform work in-place