dataflow analysis: don't depend on word size during sorting of sources
dataflow analysis: don't depend on word size during sorting of sources

The comparison routine would compute the difference between two
unsigned numbers, which would result in different signs depending
on the machine word size.

Signed-off-by: Sven Verdoolaege <e5350bbed4977f5eb8ae1dc6abd9ae59d21ace75@kotnet.org>

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