%b would be bad because it's ANSI space, not implementationspace.  %B would
be potentially bad because it's intuitive for Binary.  I would reccommend
%D and %U for "largest type", but I think the <inttypes.h> people (who
havegotten intmax_t added to the standard) may have solved this already.

Next time I get a current draft, I can suggest upwards-compatible solutions.

-s