remove_source(name)                      source exists
	remove_sourcetbl
	remove the binaries?? but how?
upgrade_source(dpkg_source)              source may exist
	remove_source(src->name)
	add the new source to the table thing
	foreach arch, binary: add binary to arch pkgs
upgrade_architecture(dpkg_source, arch)  source exists, binary may
	find source
	foreach binary in <arch>: remove it
	foreach binary in new <arch>: add it

(remove_architecture, upgrade_source_only; could also be used, theoretically)