Bug#641153: document Built-Using field for binary packages

[Ansgar Burchardt <ansgar@debian.org>]

Charles Plessy <plessy@debian.org> writes:
> here is a proposed patch that uses a slimed version of the paragraphs proposed
> by Russ (quoted below) and keeps the original examples.

Looks good to me; seconded as well and thanks for your work.

> I agree with Russ that a binary/binary relationship may be preferrable.  For
> instance, it might avoid rare corner cases when depending on a source package
> that was binNMUed.

That would be needed if one wants to be able to recreate the same
binary, but we only want to document what is required to obtain the
complete corresponding source.  For this binNMUs of the packages used
should not matter.

Regards,
Ansgar