We intentionally provoke an early wrap of our segment_n unsigned int.
The previous code is fine according to
http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1570.pdf
"A computation involving unsigned operands can never overflow...",
but nevertheless we don't want to trigger Flexelint warnings.

Thanks to Dag Haavi Finstad for digging the ISO standards url.